Blowlamps: The PRIMUS Date & Number Coding System, a brief history of the PRIMUS name, and a short guide to identification, c1895 to c1922.

This is an article that was originally produced for the Blowlamp Society publication, Blowlamp News. In the light of further research, it has been revised, adapted and extended for website publication. It is written from the perspective of the blowlamp, but has relevance to pressure stoves or pressure lamps. Those with Primus blowlamps (or indeed pressure stoves or pressure lamps) amongst their collections, or with particular knowledge, will no doubt be able to point to various errors and omissions. As such, any feedback or corrective information will be welcomed.

Contents

Back to the Blowlamp Homepage

Overview: Early History and Background

The Primus Name & Trademark before 1911

The range of blowlamp models thought to be produced initially, from c1895

Typical markings on Svensons / B A Hjorth blowlamps c1895 / 1896, and to 1911

1911: Primus Date Codes, Model numbers and the "Cooking Apparatus" trade mark

Examples of blowlamps, markings, and date codes, 1911 to c1921

The introduction of Primus Number Codes c1922, and more on the Date Codes

Examples of date and number codes

Primus Date Code Chart (generally accepted)

Notes & References, Sources of Information, and Acknowledgements

     

 

Overview: Early History and Background 

The name Primus is generally synonymous with the portable pressure stove, and so to begin with it is helpful to consider Primus blowlamps within this context.

This brief overview looks at the Primus stove, the start of J V Svenson / B A Hjorth blowlamp production, and the introduction of the Primus date code, model numbers, and the Primus number code.    

The PRIMUS Stove

The invention of the first paraffin (kerosene) wickless pressure stove is generally attributed to Frans Wilhelm Lindqvist and, in part, to his brother, Carl Anders Lindqvist whilst working at AB Separator in Stockholm during the late 1880s and the beginning of the 1890s. Some attribution for its earlier development has been given to Ludwig Holm1, a fellow employee at AB Separator, but his work was never fully recorded. The Dane, Frederik Ferdinand Tretow-Loof 2 has by some been credited with the invention; if this was the case, it was said to have been later sold to F W Lindqvist.

The main feature of the new stove was that the paraffin was pressurised in the tank, and pre-heated within the burner, so that it was vapourised prior to combustion. This increased the heat capacity, reduced paraffin consumption, and greatly reduced the amount of smoke and soot.   

So in March 1892, in Stockholm, F W Lindqvist formed a partnership with factory owner Johan Victor Svenson, to begin the production of kerosene pressure stoves, albeit on a small scale. The company was named J V Svensons Fotogenköksfabric (kerosene stove factory) and the stove was given the brand name Primus. In that same year, a patent for (or improvements to) the stove's burner was taken out by J V Svenson3 (with F W Lindqvist as inventor). This was Swedish Patent SE3944.

Berndt August Hjorth, whose tool & engineering firm, in partnership F H Getzmann, was begun in Stockholm in 1889, quickly became interested in Svenson’s product and a contract was signed in August 1892 giving B A Hjorth sole global marketing rights. Initially, exports of the Primus stove and associated cooking apparatus were to Norway, possibly by the latter part of 1892. By the end of 1893 exports extended to Russia, England and to the wider world through Hjorth's business and export contacts in Hamburg

It is also believed that stoves and associated cooking apparatus were being marketed in America as early as 1893, all of which resulted in the need for increased production capacity, and so in the same year new premises were obtained in Kungsholmen, Stockholm.   

The start of J V Svenson / B A Hjorth Blowlamp Production

In what is thought to be 18954, J V Svenson / B A Hjorth took up the production of blowlamps based on what are generally accepted as the designs of C R Nyberg5 and the Max Sievert blowlamps in production at the time, as well as Lindqvist's own ideas and designs, of particular relevance to blowlamps being the 1893 Swedish Patent SE5102, of J V Svenson (with Lindqvist as inventor). This was for a "Burner for petroleum heating apparatus" 6. In addition, some of Svensons first blowlamp types (notably the Vesuvius) utilised a burner, originally designed for a stove, which was effectively that of Lindqvist's patent SE3944.

Exports of B A Hjorth blowlamps would have followed the pattern already established for stoves and associated cooking apparatus. As early as 1896, for example, Primus blowlamps and plumber's furnaces were being retailed in America by the Primus Cooking & Heating Apparatus Company.7

In 1898 the Svensons factory reorganised as a limited company under the name Aktiebolaget (AB) Primus. In 1904 J V Svenson retired, whilst  F W Lindqvist remained as CEO and sole director of the company, and in 1906-07, Lindqvist had larger facilities constructed on the island of Lilla Essingen in Stockholm. In a catalogue from 1907, they claimed to have been the biggest blowlamp manufacturer in the world.  

A number of patents8 were taken out in Sweden, and other countries, in the 1880s / 90s and the early 1900s by J V Svenson (with F W Lindqvist as inventor), C R Nyberg, Max Sievert and others, with ideas and developments for both the pressure stove, the blowlamp, and related apparatus. 

1911: The PRIMUS Date Code and Model Numbers introduced

In 1911 there were changes to the markings on blowlamps. In particular, the Primus date code was introduced, but thought to be on paraffin models only. See below. Also model numbers11 were introduced which generally appeared on the tank shoulder, alongside the model name. It is thought the model name had been present since the outset of production in c1895. 

Also in 1911, the "cooking apparatus" trademark started to appear on the tank, above and in addition to, the "soldering equipment" trademark. The "soldering equipment" trademark is thought to have been introduced in c1896 shortly after the start of blowlamp production in c1895. See below.

In 1918 F W Lindqvist sold his share in Aktiebolaget (AB) Primus to B A Hjorth; and the Primus brand became a company in its own right as part of the (AB) B A Hjorth & Co group (which had become a shareholder company in 1916) and which was later to be known as BAHCO9. Again,  changes to the markings on blowlamps probably took place at about this time. See further discussion below.  

c1922: PRIMUS Number Codes introduced

In c1922 Primus number codes, see below, were introduced, which always appeared with a date code. Date codes (introduced in 1911) continued to appear on stoves until 1963; and on blowlamps until at least 1956. Number codes (as such) on both blowlamps and stoves seem not to appear after c1956. The known range of numbers is 1 to 39.

 

The PRIMUS name & trademark before 1911 

Primus Mark ~ thought to be on Stoves until 1896

It is thought that the very earliest Lindqvist / Svenson pressure stoves, before B A Hjorth's involvement in 1892, had no markings on them apart from that on the filler cap (and in some cases the pump cap) which was stamped F W Lindqvist Patent 10 . However, the Primus name left without the stylised stove between Pri and Mus, was seen on stoves from as early as 1892, probably when B A Hjorth acquired the marketing rights. This style of the name, imprinted on the stove's tank shoulder, was thought to have been in use until 1896, at which time it is assumed to have been replaced by the familiar Cooking Apparatus trade mark below left.

In the case of blowlamps, it is probable that the soldering equipment logo lower left was introduced in 1896, and not at the outset of blowlamp production in what is believed to be 1895, as there are examples of paraffin blowlamps with just the wording "B A Hjorth & Co, Stockholm, Sweden" stamped into the underside of the tank, and with just the model name stamped onto the tank shoulder. Such early blowlamp examples rarely appear. Indeed, it may be almost impossible to identify the very earliest of the petrol models. See below for further discussion. 

The B A Hjorth catalogue of products dated 1898 illustrates both the Cooking Apparatus trade mark, and the Soldering Equipment trade mark. See extract (French version).     

Prior to 1911 no model numbers as such appear on blowlamps11 rather, model types were identified by the names Aetna, Effectiv, Nautilus, Ultraprimus, Petrolia, Tarantella and Vesuvius, which were all designed to run on paraffin. Whilst the Phoenix (a self-heating soldering iron) the Ideal, (for drying of foundry molds etc), (the) Swedish Lamp12, and Vulcan models were all designed to run on petrol

The range of blowlamp models initially produced is difficult to determine due mainly to the lack of trade literature prior to 1898 but would have included at least some of those models listed. See below and the extract from the B A Hjorth 1898 catalogue. It is thought that the Nautilus, Petrolia and Tarantella models (all paraffin) were not part of the original range, but that they appeared some time before 1911, although this cannot be established in the case of the Tarantella

The "Cooking Apparatus" trademark, and hence the name "Primus" first appeared on J V Svenson / B A Hjorth blowlamps in 1911, and was in addition to the "Soldering Equipment" trade mark.

1911 is also the year in which Primus model numbers and date coding started to appear on blowlamps. See below.

Two sizes of the "Soldering Equipment" trade mark were used, with small detail differences. Both sizes of logo can be seen on examples of the Swedish Lamp (immediately below) so tank size appears not to have been relevant. The larger size is not so often seen, and was perhaps only used over a particular period, or on certain export models? Certainly, the smaller of the two marks appears to be that which is generally seen.

Cooking Apparatus Trade Mark ~ 1898 catalogue  

Soldering Equipment (blowlamps) Trade Mark from the 1898 catalogue.  

It is a possibility that the soldering equipment logo was used on blowlamps from 1896, and not the outset  of blowlamp production  in what is believed to be 1895, whilst it is probable that the logo was no longer employed after 1918 when (AB) Primus was acquired by B A Hjorth.

"The Swedish" blowlamp (left) from the B A Hjorth 1898 catalogue. This model was used to illustrate the familiar "two blowlamps" Soldering Equipment logo. Two sizes of the logo are shown here on examples of "The Swedish Lamp". The smaller of the two is that which is generally seen. 

 

The range of blowlamps and related "soldering equipment" thought to be produced initially, from c1895  

"The Swedish"  "Aetna"  "Vesuvius"  "Effectiv" 

"Vulcan" 

"Phoenix" (top) & "Ideal"   

"Ultraprimus" 
Petrol Paraffin Paraffin Paraffin Petrol Petrol Paraffin

The above models are listed in the B A Hjorth 1898 catalogue (see extract). It is therefore assumed that some, if not all, were produced from c1895. The "Aetna", "Vesuvius", "Effectiv" and "Ultraprimus" models were designed to run on paraffin, whilst "The Swedish", "Vulcan", "Phoenix" and "Ideal" models were intended for petrol. 

The "Petrolia", "Nautilus" and "Tarantella" (all three intended for paraffin), although early models, are probably slightly later. The "Petrolia" and "Nautilus" models very likely appeared before 1911. There is doubt regarding the "Tarantella". More research is required.

There were a number of configurations of most of these models but that is outside the scope of the article 13 . The "Ultraprimus" was essentially a stove adapted for use as a soldering and melting furnace, and therefore, like blowlamps, came within B A Hjorth's "Soldering Equipment" range.

 

Typical markings, thought to be the earliest, 1895 / 1896, Aetna, Vesuvius (and other paraffin?) models

From c1895, in the case of Aetna and Vesuvius models, and for approximately the first year of blowlamp production, a particular set of marks appears (immediately below). The same or similar markings probably appeared on the other paraffin models from this first period, but it is not known due to the scarcity of examples. The marks comprised the wording "B.A.HJORTH&Co, STOCKHOLM, SWEDEN" on the underside of the tank, the model name on the tank shoulder, and "F.W.LINDQVIST, PATENT" on the pump cap. 

There is some doubt as to the marking (if any) on the filler cap of these very early paraffin models. Those models designed to run on petrol had a different design of filler cap, a "wingnut" type, as can be seen on the illustrations of the Swedish and Vulcan models above. See also below

In any case, it is not known for certain how the very first petrol models were marked. Indeed, as previously mentioned, unlike paraffin models, it may be almost impossible to identify the very earliest of the petrol models.

Above left. This mark, examples of which have been seen on the underneath of the tanks of both Aetna and Vesuvius blowlamps, is probably the earliest, and thought to date to the start of blowlamp production (1895?). Where this mark is found, the only other marking to the tank is the model name on the tank shoulder, as in the case of the Aetna above. Examples of blowlamps with such markings do not appear that often.

Note also that the Aetna example above has a "blank" filler cap, and whilst there is nothing to say this is not original, the filler cap to the right is that which might be expected, but it is argued (and rightly so) that a filler cap is not a reliable means of evidence, as it can be lost and replaced with something non-original. The pump cap will very likely be marked "F W Lindqvist, Patent", as the example above shows, but the same caution should be applied here as it does to filler caps. 

In the case of stoves, this same mark (above left), which (like the Aetna and Vesuvius blowlamp examples) is seen on the underside of the tank, is also probably the first "B A Hjorth" mark used on stoves, from as early as 1892, probably following Hjorth's acquisition of the marketing rights. As it is assumed that this mark was no longer used on paraffin blowlamps after c1896, it is thought the same applied to stoves. 

 

Typical markings, thought to be c1896 to 1911 (on filler caps, to c1918?)

The next two sections describe the markings to the tank bodies of B A Hjorth paraffin and petrol models respectively, as there were variations. The section immediately following then looks at those items which were removable, the filler caps, pump caps, and pressure release screws.

The only notable change during the period 1896 to 1911 is to the wording to the circular marks seen on either the tank shoulder or the underside of the tank, and the wording to the filler cap. It is possible this change took place in c1898 at the time the Svensons factory reorganised as a limited company under the name Aktiebolaget (AB) Primus, and the wording "AktBol" or A/B (Aktiebolaget) introduced. This is difficult to judge without sight of a large number of samples; even then, there may be no clear date delineation between the different markings. Further research and information is required

Typical markings on the tank body, paraffin blowlamps, thought to be c 1896 to 1911 

The examples of marks shown above are those generally seen on paraffin models of blowlamp between c1896 and 1911.

Left. The Svensons / B A Hjorth familiar Soldering Equipment trade mark. This example is from a Vesuvius. It is thought this mark appeared on both paraffin and petrol models throughout the period in question. But see note 15 with reference to "Phoenix" and "Ideal" models (self-heating soldering irons).

Centre left. The B A Hjorth circular logo seen on the underside of those paraffin blowlamps considered to have been produced between c1896 and 1898, though these dates are by no means certain.

Centre right. The wording "AKTBOL" (Aktiebolaget) is present, dating such examples to between what is thought to be c1898 and 1911. Note that it is difficult to be precise about these dates.

In 1911 this circular logo was adapted (on paraffin models) to include the date letters assigned between 1911 and c1921. See examples below. This particular circular logo is believed not to have been used on petrol models of blowlamp. 

Right. There were no model numbers until 191111, but  model names were still to be seen, generally on the tank shoulder, as with this Vesuvius example. Model names appeared from what is thought to be the outset of production in 1895, see above). The model name on the tank shoulder applied to both paraffin and petrol models. For further examples see below.   

 

Typical markings on the tank body, petrol blowlamps, thought to be c1896 to 1911

Above. The B A Hjorth circular logo, invariably on the tank shoulder of petrol models (with the exception of the Petrolia*) and seen up until what is thought to be 1911. It therefore follows that for any given model (petrol or paraffin) there was either the circular logo on the shoulder of the tank, or that seen on the underside of the tank, but not both. A number of variations are shown; note on the left that "AktBol" (Aktiebolaget) is not present as on the other examples. As discussed, this is thought to put this particular mark as being in use up to 1898 (see above) at which time the Svensons factory reorganised as a limited company under the name Aktiebolaget (AB) Primus, although this is open to further research.

Left. The Svensons / B A Hjorth familiar Soldering Equipment trade mark. This example is from a "Swedish Lamp". It is thought this mark appeared on both paraffin and petrol models throughout the period in question.

As discussed, until 1911 there were no model numbers on blowlamps, but model names were generally imprinted on the tank shoulder, in some cases along with the circular logo. See examples below

*The Petrolia had a screwed access plug in the underside of the tank, so that the circular logo associated with paraffin models could not be imprinted on the underside of the tank. Instead the circular logo, normally employed on the tank shoulder of petrol models, was used as in the example below.

 

Typical markings: removable items, thought to be c1896 to 1911 (filler caps, to c1918 or later?)

Above left. These two examples of filler caps are typical of those found on the paraffin models. In the absence of more information it is possible that the change between the markings on these two caps took place in 1898 at the time the Svensons factory reorganised as a limited company under the name Aktiebolaget (AB) Primus and the wording "AktBol" or A/B (Aktiebolaget) introduced. This style of cap with its markings continued until what is thought to be 1918. As discussed above, with regard to filler caps, it is sometimes argued that they are not a reliable means of evidence, as they can be lost and replaced with something non-original. 

Middle right. Filler cap, typical of those used on the petrol models. These have no makings. This pattern of cap continued on Primus petrol blowlamps until what is thought to be the mid-1920s. 

Above right. Possible variations aside, the pump cap will very likely be marked "F W Lindqvist's Patent", but the same caution should be applied here, with regard to originality, as it does to filler caps.

Left. Two examples of the familiar pressure release screw on the paraffin models. 

Variations exist, but on at least one side "Primus" is normally seen, as on the example, far left. The example to the right has no marks, and is to be found on a pre-1911 Vesuvius. The type with the name may not have been in use until after 1911?

Examples without any markings are quite often seen on stoves from c1892, and on the very early models of blowlamp. Again, the same caution should be applied here, with regard to originality, as it does to filler caps and pump caps. 

 

B A Hjorth blowlamps, up to 1911. Model names on the tank shoulder, but no model numbers or date codes

Examples of Svensons / B A Hjorth paraffin and petrol blowlamps up to 1911, without model numbers or date codes. Note the Swedish Lamp (bottom right) also has the name imprinted in German "Die Schwedische Lampe", presumably for distribution within Germany. 

Shown are Petrolia (paraffin), Vulcan (petrol), Aetna (paraffin), Vesuvius (paraffin) and The Swedish Lamp (petrol.)

 

1911: The introduction of Primus Date Codes and Model numbers, and the addition of the Primus "Cooking Apparatus" trade mark.

Primus date coding started in 1911 and continued until what is thought to be1963. This applied to paraffin stoves, paraffin blowlamps, and possibly pressure lanterns. It is thought that date coding on petrol blowlamps started in c1922. 

The generally accepted date code chart is shown below. With this chart, the codes "I" and "AI" are used rather than the codes Q and AQ which are now considered never to have been used. There is more on the date codes below.

From 1911 (probably to 1918, when Svensons was wholly acquired by B A Hjorth) blowlamps were stamped with both the PRIMUS (cooking apparatus) trade mark and the Svensons / B A Hjorth (soldering equipment) trademark, as both an Aetna 632 example with the date code A for 1911, and an Aetna 634 example with the date code D for 1914 (just below) illustrate. Certainly by 1920 the Svensons / B A Hjorth "soldering apparatus" trade mark is no longer present, as an example (below) of a 1920 model 651 (date code J) indicates. It is not known why the "soldering apparatus" trade mark was discontinued at this time, especially as it had appeared exclusively on blowlamps from what is thought to be c1896. See above. However, the PRIMUS (cooking apparatus) trade mark continued to appear on blowlamps until what is thought to be c1936. Thereafter, different markings were used, generally the name Primus always appears, whilst later, model numbers were pressed into the steel handle, or continued to appear on the tank side, depending on the model. However, as discussed, a description of the later years of the PRIMUS brand, and a catalogue of all the types and model numbers  is outside the scope of this article13

As discussed, model numbers also started to appear on  blowlamps in 1911, whilst model names continued to appear with numbers (see examples below). It is by no means certain when the model names / numbers combination was dropped, and replaced with just the model number, however it was possibly 1918, to coincide with the acquisition of Aktiebolaget (AB) Primus by the (AB) B A Hjorth & Co group. It can be assumed that this change had occurred by 1920, as the model 651 example below illustrates. 

So from c1918 onwards, until in fact c1936, the name Primus followed by the model number was generally imprinted on the side of the tank as the 651 example illustrates.

Quite why the Primus (cooking apparatus) trademark, date codes, and model numbers all started to appear on blowlamps in 1911 is not clear. There is no information found to date about events within the Company in 1911 that offers an explanation. We can perhaps surmise that the Primus (cooking apparatus) trade mark - previously allocated to stoves from as early as 1896 - was so widely recognised that it was thought that its appearance on blowlamps would be an enhancement, with more universal product recognition. Similarly, date codes (on paraffin models only) and model numbers may have been seen as necessary for identification and differentiation purposes with an ever increasing product range, not only by Primus itself, but its Swedish competitors, mainly Max Sievert, Optimus and Radius, and also competitors within Europe, particularly Great Britain, where manufacturers were basing a number of their designs on the Primus and Sievert models.

In c1922 (see below) Primus number codes were introduced, which always appeared with a date code. Date codes (introduced in 1911 on paraffin models of blowlamp) continued to appear on paraffin and petrol models of blowlamp until at least 1956, and on stoves until 1963. Number codes on both blowlamps and stoves seem not to appear after c1956

Date codes on petrol models of blowlamp were probably introduced in c1922, possibly at the same time as the number codes.

Examples of blowlamps, markings, and date codes, 1911 to c1921

Primus Aetna 632 with date code "A" for 1911

Primus Aetna 632 (1911) with date code A, on the underside of the tank, with both the Svensons / B A Hjorth (soldering equipment) and PRIMUS (cooking apparatus) logos, as well as the stamping “A/B B.A.HJORTH & C0, STOCKHOLME, SOLE MAKERS OF THE GENUINE PRIMUS APPARATUS, with the same wording in four different languages directly below. The year 1911 saw the introduction of both date codes (on paraffin models) and model numbers. 

Primus Aetna 634 with date code "D" for 1914

Primus Aetna 634 (1914) with date code D, on the underside of the tank, with both the Svensons / B A Hjorth (soldering equipment) and PRIMUS (cooking apparatus) logos, as well as the stamping “A/B B.A.HJORTH & C0, STOCKHOLME, SOLE MAKERS OF THE GENUINE PRIMUS APPARATUS, with the same wording in four different languages, as the 632 example above.  

Primus (Vesuvius?) 651 with date code "J" for 1920

Primus 651 (1920) with the date code J, on the underside of the tank. The Svensons / B A Hjorth two blowlamps (Soldering Equipment) trade mark is no longer present, although the stamping “A/B B.A.HJORTH & C0, STOCKHOLME, SOLE MAKERS OF THE GENUINE PRIMUS APPARATUS, with the same wording in four different languages below still appears, all below the "PRIMUS No 651" stamping. The PRIMUS (cooking apparatus) logo was also still present (on the opposite side of the tank) and thought to have still been seen on the side of tanks until as late as 1936. See above.

Note also that by this time, as this particular 1920 model suggests, the handle is the (later) pressed metal type. It is possible that the changes which this example illustrate took place in 1918 (date code G) when Svensons was wholly acquired by B A Hjorth. See above.  

Examples of date codes, found on the underside of tanks of paraffin models of blowlamp (and stoves) 1911 to c1921

Examples of date code stampings, found on the underside of the tanks of paraffin models of blowlamp and stoves (and believed to be also lanterns). Note that the "AktBol" or Aktiebolaget (A/B) (limited company) mark is present.

These examples range between 1911 (date code A) and 1921 (date code K). Blowlamps (both paraffin and petrol) from what is believed to be 1922 - and with the combined date & number code - generally have the marks stamped within a small circle on the side of the tank towards the base (see below) whilst pressure lanterns and stoves continued to be stamped, with the combined date & number code, on the underside of the tank until what is thought to be c1956.

(In the case of stoves, a similar mark appears to have been used later in combination with a combined date and number code. See below.) 

Examples of blowlamps with both model name and model number, 1911 to (probably)1918

Aetna No 632 & No 634; Petrolia No 61 (615?); Tarantella No 607; The Swedish No 855, and Effectiv No 681. Examples of the format, with both model name and model number, from 1911 to (probably) 1918.

 

The introduction of Primus Number Codes, c1922, and more on Date Codes

A number starts to appear, always with the date code letter, in what is believed to be 1922 at the earliest. Certainly, a range of different numbers for both stoves and blowlamps start to appear in 1923 (data for pressure lanterns unknown) and continues, in the case of blowlamps, until at least 1953; and in the case of stoves, until at least 1956. Over the period that these numbers appear, numbers ranging between 2 and 37 have been noted for blowlamps, and between 1 and 39 for stoves.

Observational studies14 of available date codes and associated numbers, for both blowlamps and stoves, have been carried out which give an indication of the distribution of numbers used over time. However, because this represents such a small sample, compared to the vast number of actual blowlamps and stoves produced, nothing positive - statistically - can be deduced. In addition, the meaning of the numbers has been the subject of considerable speculation and has not yet been satisfactorily explained. What we can say is:

a. Some later date codes on blowlamps appear without a number. Where this occurs, as far as is known, the date code is always to be found on the underside of the tank. See examples immediately below. Note the "AT" example has space beneath for a number. This space beneath is also seen on "AS" examples. In addition, Primus 71 stoves have only been seen with a date code (no number), again on the underside of the tank.

b. The number, where present, is only ever seen with the date code letter. A number never appears on its own.

c. For any given year that numbers appeared, probably the same range of numbers (say 1 to 39) would have been available 14.  

With the paraffin models of blowlamp that had a date letter within the B A Hjorth circular logo (1911 to at least 1921 above) the logo was centrally positioned on the underside of the tank. Paraffin blowlamps, pressure stoves and (it is believed) lanterns were stamped thus. Both paraffin and petrol blowlamps after this - with the combined date & number code - have the marks stamped within a small circle on the side of the tank towards the base, whilst pressure lanterns and stoves continued to be stamped, with the combined date & number code, on the underside of the tank until c1957.

In the case of stoves, it is thought that by 1955 a six-digit numerical code was in use, with the last two numbers denoting the year, although the date codes AU and AV continued to be used. The significance of the first four digits of the six digit code is not known. The six digit code was to be found on one of the stove's legs, the burner riser tube or the pump housing, depending on model. Several examples of such markings on stoves can be seen on the Classic Camp Stoves Site. After 1963 codes may have been included (until date?) on the outer packaging rather than the item itself.

To further complicate matters, one source describes that in 1953 (AS) until (and including) 1956 (AV) number codes were replaced with letters H, Z, HZ, FZ and a number / letter combination 4Z, 5Z, 7Z (and possibly others), such that examples AT over Z, AU over Z, AU over 5Z, AV over 4Z, AX over FZ etc are noted on pressure stoves (Classic Camp Stoves website). Again, without further examples it cannot be said for certain if this later change to the coding applied to blowlamps, but there is nothing to say it didn’t.      

 

Examples of date and number codes on blowlamps

Date codes without a number code are thought always to be seen on the underside of the tank. This is the case with the aforementioned model 71 stove. 

Note the "S over 20" and the "AT" examples are both from a model 854 blowlamp, but with 26 years between.

M over 21 (1923) on the tank side of a model 632. Note the "M" almost an upturned "W"

O over 8 (1925) on the side of the tank of a model 631

P over 9 (1926) on the side of the tank of a model 619

S over 20 (1928) on the side of the tank of a model 854

X over 9 (1933) on the side of the tank of a model 615

T over 9 (1929) on the side of the tank of a model 618

AP (1944) with no number, and central within circle, on the underside of the tank of a model 630

AC (1938) with no number, and central within circle, on the underside of the tank of a model 801

AT (1954) with no number, and to top of circle, on the underside of the tank of a model 854

Y over 9 (1934) on side of the tank of a model 862

 

Stoves: A variation?

Stoves: A variation? These two examples of date and number codes, V over 29 (1931) and Z over 11 (1935) from the underside of stoves, are accompanied by the B A Hjorth circular logo considered to be in use between 1898 and 1911. See above. The inclusion of the circular logo on stoves after c1922 does not appear to be common, but the exact extent is beyond the scope of this article.

 

Primus Date Code Chart (generally accepted)

 (Adapted from Pressure Lamps International, and Classic Camp Stoves websites)

A    1911

B      1912

C    1913

D    1914

E    1915

F    1916

G    1917

H      1918

I      1919

J    1920

K    1921

L    1922

M    1923

N      1924

O    1925

P    1926

R    1927

S    1928

T     1929

U      1930

V      1931

W    1932

X    1933

Y    1934

Z     1935

AA   1936

AB   1937

AC   1938

AD   1939

AE   1940

AF   1941

AG   1942

AH   1943

AI     1944

AJ   1945

AK   1946

AL   1947

AM   1948

AN   1949

AO    1950

AP   1951

AR   1952

AS   1953

AT    1954

AU or ****55    1955

AV or ****56   1956

****57   1957

****58   1958

****59    1959

****60   1960

****61   1961

****62   1962

****63   1963

 

 

Notes

1. For further discussion of Ludwig Holm see "Från Klara till Kosmopolis" (From Klara to the Entire World) by Ivar Anell, Stockholm, 1929.

2. For further discussion regarding Frederik Ferdinand Tretow-Loof see http://translate.google.co.uk/translate?hl=en&sl=da&u=http://tegl.info/Historie.htm&prev=search for example.

3. One source reports that the Lindqvist brothers were granted a patent for their "new stove" at the "end of the 1880s", whilst another gives the date for this patent as 1891. However, a patent for a complete "new stove" is not known, so the patent in question is considered to be Swedish number SE3944 (1892) of J V Svenson (with F W Lindqvist as inventor) which is a design for, or improvements to, the stove's burner, which became known as the "roarer" type, and which remains virtually unchanged to this day. The development of the "silent" burner, which can be differentiated from the "Roarer" burner (the subject of the earlier patent SE3944) is open to speculation and discussion. Carl Anders Lindqvist took out a patent for a pressure stove burner SE10872 in 1898, which is possibly the forerunner of the "Silent" burner, but other patents, including those of J V Svenson (with F W Lindqvist as inventor), C R Nyberg, and others could also be considered.

4. Very little, if any, information can be found to verify the date of 1895 as being the start of Svenson's blowlamp production. One example (although arguably obscure) is from "Two Planks and a Passion", Page 314 (Roland Huntford, 2008) where the "Primus Blowlamp" was described for the purposes of ski-waxing. See https://books.google.co.uk/books?isbn=1441134018

5. The collaboration between C R Nyberg and Max Sievert is well documented. C R Nybergs Lampfabrik (lamp factory) had been the first company producing blowlamps in Sweden from as early as 1882, and by 1886, Max Sievert had taken on the marketing of Nyberg's blowlamps, which is probably why very few blowlamps displaying the Nyberg name appear. In addition to blowlamps, Nyberg started the production of stoves based on the Lindqvist design, at much the same time as Svensons started the production of blowlamps, believed to be 1895. Eventually, in 1922, A B Max Sievert took over the company of C R Nyberg. 

The earliest of C R Nyberg's recorded Swedish patents is 1891, for a hand fire sprayer (brandspruta). No known patents exist for Nyberg's early development work on prototype blowlamps as much of it pre-dated the Swedish patent system which was initiated in its current form in 1885, although it has been noted that Nyberg obtained a patent for his first prototype blowlamp (or "soldering blowtorch") in 1882, which pre-dates the "modern" Swedish patent system, and so we have no written record or description of this patent. See https://en.wikipedia.org/wiki/Swedish_Patent_and_Registration_Office. Max Sievert took out a patent in Great Britain (and elsewhere?) in June 1887, patent GB08643, which covered a number of features for improvements to C R Nyberg's blowlamps. This patent indicates the advanced state of Nyberg's blowlamp designs at this time. Of note also is that C R Nyberg took out patents SE4982 in 1893, and United States patent US596084 in 1897, both for a hydrocarbon burner device (one for a blowlamp, the other for a stove) specifically to facilitate the cleaning of the burner tubes.

6. Although the patent SE5102 itself describes a method for pre-heating the fuel and improving the flame within the burner, it appears to be a prototype for blowlamps fuelled by paraffin, the design of which was later adopted by many other manufacturers, both in Sweden and other countries. B A Hjorth also took out this patent in Great Britain in May 1984, patent GB09819.

7. In the early 1900s Primus products were marketed through both the Globe Gas Light Co, Boston, and A E Lovett Co of New York. Lovett claimed to have made "Primus" paraffin blowlamps in America (Vintage Blowtorches, by Ronald Carr, Charles Smith, Graham Stubbs, 2007). Almost immediately after the granting of his Swedish patent SE3944 in November 1892, J V Svenson took out the equivalent patent in America US500781 which was granted in July 1893. Although essentially the same, there are small detail differences between the two patents.

8. Swedish patents can be viewed at http://was.prv.se/spd/search?lang=en. See also the list of Swedish patents relating to blowlamps / blowtorches & associated equipment. Please note however that this is intended as a guide only, and is based on a search of the Swedish Patent database, whereby all of the patents listed are in Swedish, and as far as is known, have not been translated into English. This creates difficulties for anyone without a sound knowledge of the Swedish language, particularly Swedish technical language.

9. B A Hjorth acquired 100% of Svensons in 1918, and hence the Primus trade mark, and located his holding company on Lilla Essingen, in Stockholm, the location of Aktiebolaget (AB) Primus since 1906-07. The company grew by mergers, but it is believed that it was not until 1954 that the brand name BAHCO was first used. BAHCO, is an acronym of the original name B A Hjorth & Co. See http://en.wikipedia.org/wiki/Bahco      

10. Generally speaking, the very earliest Svensons / Lindqvist stoves prior to either the founding of J V Svensons Fotogenköksfabric in March 1892, or the acquisition of marketing rights by B A Hjorth (August 1892), had no name on them apart from that on the filler cap, or sometimes the pump cap, which were stamped F W Lindqvist Patent. More than one patent number is recorded as being seen on the filler caps of the early F W Lindqvist stoves. One is patent number 394 (assuming it to be Swedish, and dated 1885) but does not refer to anything stove related. It is possible that a fourth digit has been rubbed / omitted from the filler cap, in which case the number could be 3944, which is the  Svenson / Lindquist patent SE3944Another such patent is 6186, but if this is taken to be Swedish (SE6186) it has no reference to stoves; rather it refers to a type of (nail) fixing. 

11. Single and double digit model numbers appear with what is believed to be most of the model names in the B A Hjorth catalogue of 1898 (left, click on to enlarge). These early model numbers, which were used to differentiate tank capacities, burner configuration, or particular features, as far as is known, never appeared on the blowlamps themselves. It is thought that model names, from the outset of blowlamp production, were initially imprinted on the tank shoulder. Model names together with model numbers, started to appear in 1911. Model names (with possible exceptions?) on blowlamps no longer appeared after what is possibly 1918, which saw the acquisition of Aktiebolaget (AB) Primus by B A Hjorth, at which time the Primus brand became a company in its own right as part of the (AB) B A Hjorth & Co group. As a result of this change it is reasonable to assume that the Primus "soldering equipment" trademark no longer appeared. The word "PRIMUS" followed by the model number (on the side of the tank) was the generally seen replacement, whilst the Primus "cooking apparatus" trademark continued to appear on the opposite side of the tank until what is believed to be 1936.

12. The Swedish Lamp. It might be surmised that the Swedish Lamp was the first to be produced by Svensons, given it’s similarity in design and function to the Nyberg prototype, and the name Swedish Lamp a way of establishing a generic type (possibly free of patents) and / or as a way of acknowledging Nyberg’s achievement and – it goes without saying – its country of origin. The name Swedish Lamp was also later given to similar models produced by Optimus, Erikssons (and others?) and possibly also to versions with no manufacturers name, but produced in Sweden, and possibly Britain, intended for resale and re-marking or rebadging with stockists or retailers names or brand names; possible examples of this are Wilfin, Lux, Willander and Beanco. It is also worth noting that the B A Hjorth Vesuvius employed a version of the Lindqvist patented "stove" burner, to run on paraffin, and therefore could have been an early model in the B A Hjorth range, possibly superseded by the burner in the Svensons / Lindqvist 1893 patent SE5102, although the "stove" burner - in adapted forms -  was employed on Vesuvius as well as a number of other B A Hjorth / Primus blowlamps for many years.

13. Since the introduction of model numbers in 1911, various series of numbers were employed over time, most notably the 600 series for paraffin models, the 800 series for petrol models, and the 700 series for industrial or household "Heating Apparatus". There are other number series but the exact range of model numbers, and the periods for which individual model numbers were used, is outside of the scope of this article. As such, this article does not attempt to catalogue or list all the various blowlamp types, model names, and model numbers that have been produced under the B A Hjorth / Primus name. With a few exceptions, any Primus blowlamp manufactured between 1911 (c1922 for petrol blowlamps) and c1956 (or stoves between 1911 and c1963) can be dated by inspection of the date code on the tank.

14. Date and number codes observational study. Note that this represents a very small sample, compared to the vast number of actual blowlamps and stoves produced, and as such nothing definitive can be deduced, and due caution should be exercised in the interpretation of the data.

15. In the absence of examples of "Phoenix" and "Ideal" self-heating soldering irons from the early period, it cannot be determined what markings appeared on these models. And although based on very limited information, no date coding has been noted on Primus self heating soldering irons. Were in fact Primus self heating soldering irons ever date coded? If so, what form would the code have taken, and where would it have been positioned?  

Copyright: A note from the author.

For articles such as this, where it is impractical to gather all the information from primary sources, much of the material, including a number of illustrations and photographs, is sourced from the Internet. However, such information, from whatever source, should not simply be "cut and paste" (unless clearly noted as such, and acknowledged). Copying such "blocks" of information is effectively plagiarism; it can take such information out of the context in which it was originally intended, which can mislead and sometimes compound errors. Where possible, the principle of "fair use" of information is herewith employed. However, copyright laws do exist for very good reasons, and the owner of photographic or written material has every right to object to its "re-use" for whatever reason. If anyone objects to the use of any information or illustrations within this article, or indeed anywhere on this website, please make this known and it will be rectified as soon as possible.

Sources of information and acknowledgements

Classic Camp Stoves website http://classiccampstoves.com/ 

Pressure Lamps International website http://homepage.ntlworld.com/munwai/homepage.htm

Primus catalogue information kindly supplied by Graham Stubbs, Blow Torch Collectors Association http://vintageblowtorches.com/

Wikipedia (about the Primus Stove) http://en.wikipedia.org/wiki/Primus_stove

The Dictionary of Swedish National Biography http://sok.riksarkivet.se/SBL/Start.aspx?lang=en

Swedish Patent Database http://was.prv.se/spd/search?lang=en

add others..........

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Site History & Revisions

15 April 2016 First published; 31 May 2016 Minor revisions;

23 September 2016 Revised and re-published to website.

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