I had these images of an old 821 sent to me by Petri in Finland. Appears to be an early 30s or maybe even late 1920s example. I can't think of another with a collar label like this one. ::Neil::
It would be nice if he (Petri) would search for the scratched numbers in the buttom of the tank. That would tell the age more precise. It is not easy to see, but I believe the vapourizer is in one piece - so early. Claus C
As I remember from pressurelamp-school then the 2 parted vapourizer came in 1933. So both and lanterns are before 1933, just looking at the vapourizer. Then there is the print on the tank to deal with, because that changed too in the first years, but how, is unknown to me. The first 821 should appear around 1925, in theory already in 1922, according to the patent, because the patent for the lamp was brought in at the year of 1921, as I recall. Still there is a good chance to find the exact date in the bottom of the lamp, though it can be difficult to see. The name/model-plates comes in many different shapes and it could be funny to find out if there is a timeline in these. Sometimes other plates is attached as one of these: and this from 1929 with these 2 plates: Claus C
There is a 1921 patent for a table lamp but the first patent for a lantern is from August 1926. This is the first of the 4 company joint patents which incorporated the Aida patent for the Preston Loop type generator. I am not aware that Petromax made a lantern before this and I suspect it was 1927 at the earliest when they first produced a lantern of any type. I may of course be wrong here but I have seen no evidence from advertising, catalogues or patents to suggest an earlier date for the first Petromax lantern. ::Neil::