"One of those stoves you like plus a couple of other flat ones!"

BradB · Aug 31, 2018

What does the 1S mean? I have an Optimus 1S that is regulated. Is there any commonality?

shagratork · Aug 31, 2018

The Optimus No.1S is a roarer burner stove.
The Optimus 1S is shown here:

You say that your stove is regulated.

The only regulated No.1 that I can find is the Optimus 'Matador'.

However, is your regulated stove a silent burner?
If so, then the burner has been changed.

Tony Press · Aug 31, 2018

@BradB

You asked “what does No. 1S mean”?

Can you post a photo of the markings with the “No. 1S”?

In this photo from @igh371 you will see the No. 1S. The “S” signifies a more economical model of the No. 1. Both Optimus and Primus did this.

The full thread is here:

https://classiccampstoves.com/threads/optimus-no-1s-c-1912-4.34559/

Tony

BradB · Aug 31, 2018

@Tony Press Mine does not look like an economy model. Back when I got it some of the historians on the site found evidence that mine was offered in a regulated burner. Gary Adams (BernieDawg, who fettled it for me) says that it was a very early regulated model, due to the design that may have been produced only one year before it was changed. I am not the best at finding old posts here on CCS. It is not like the other regulated burners I have seen and the cleaning needle was like nothing I had seen. Of course the control knob is not original, the stove came without one.

BradB · Aug 31, 2018

I just looked at my old emails from Gary and he tracked the old catalogs down. He said mine is shown as available about 1934 or a bit earlier. The burner was made slightly wider because it was offered as a heater. I changed the riser to the shorter one. Of course, I still have the longer riser. I made the pot legs and I bought the porcelain trivet. Brad

Tony Press · Aug 31, 2018

@BradB

It would be the construction of the tank, rather than the burner, that earns it the “S” designation, I presume.

I like a good stove detective story, but I’m tied up for the next couple of days with family business.

I’m sure @shagratork ’s spreadsheet will come in handy here.

Cheers

Tony

kerophile · Sep 1, 2018

Hi, @Tony Press was correct regarding the meaning of the S and J designation on the stove model number:

https://classiccampstoves.com/threads/primus-1-s-or-1911.13557/#post-132458

These were economic versions of the Non-S. models

Best Regards,
Kerophile.

kerophile · Sep 1, 2018

Hi, here is some more information on the S and J designation used by both Primus and Optimus:

kerophile said: ↑

Hi, both Primus and Optimus made budget versions on their No.5 stoves, designated 5S.

In an Optimus catalogue I have seen it stated that the brasswork on the 5 is 25% thicker than on the 5S.

The 5 had a tank capacity of 2 pints nominal whereas the 5S is listed at 1.75 pints. They apparently saved one ounce of brass in manufacturing the 5S relative to the No.5.... An early example of "Value Engineering" !

It sticks in my mind that the "S" stands for Senior....but don't ask me why they called the inferior model that.

Best Regards,
Kerophile.
Click to expand...

abbahco1 said: ↑

The answer to the designation "S:or" lies in the Primus filler cap patent of 1919. From 1920 this patent (a recessed filler cap - see the "patents" section on this site) was applied to the original silent and roarer domestic stoves. To distinguish between these new creations (which were now designated No. 1 & No. 5) and the original models (i.e. pre-filler cap patent), the older models were retained with the designation "Senior", perhaps logically complementing the designation "Junior", which had already been introduced for 2 pint stoves with smaller burners than the standard ones. Perhaps in order to justify a higher price for the new models 1 & 5, the Senior models (stamped S:or) 1 & 5 were made of slightly lighter gauge brass (although early examples are still much heavier than later AB BAHCO models 1 & 5), while the tank capacity was usually given as 2 1/8 pints, while the new 1 & 5 models were listed at 2 1/4 pints. In fact, judging by the ratio of surviving examples, the seniors (which were for all practical purposes identical in function to the newly introduced 1 & 5 models, and which used the same quality components) remained more popular than their more expensive replacements. Post-1920 models 1 & 5 survive in far smaller numbers than the seniors. The sunken filler cap made little practical difference to the operation of filling the stove and it didn't significantly add to the tank's fillable capacity.

The last seniors were manufactured in 1955 after which the old lettering system (A-Z; then AA-AV) was replaced with a 6 digit code (ending with the two final digits of the year of manufacture from 56-64). The company stamp was changed from A(ktie)B(olaget) B. A. Hjorth & Co. to the contraction AB BAHCO. The Primus 1 & 5 models were made by BAHCO until the 1963 buy-out by A. B. Optimus, which then manufactured under the trade name PRIMUS TRADING AB, alongside identical stoves made under the Optimus and Svea (which Optimus had acquired from AB Max Sievert) names.

AB Radius (founded by former Primus workers in 1913 after a strike at Primus) adopted the same "senior" designation by the 1930s, and appears to have fairly soon got round the Primus patent (since Radius No. 1 & No. 5 stoves also featured a sunken filler cap after 1930) while AB Optimus followed suit (designating its cheaper models as 1S and 5S), although it did not gain use of the Primus sunken filler patent until 1963, when all domestic nos. 1 & 5 stoves, whether bearing the name Optimus, Primus or Svea, were in fact identical in manufacture, and all featured the sunken filler cap (which Svea had also used from the 1940s on).
Click to expand...

From this thread:

https://classiccampstoves.com/threa...n-a-primus-no5-and-a-no5-sor.5763/#post-51806

Best Regards,
Kerophile.

BradB · Sep 1, 2018

Thanks for the great info, Brad

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