Ive got what i think is a BSA standard number 2. It has a stamp on the side s2129 at first i thought it might be the last number on the first run of these, however i see info now that says s means 1919 or after. I havent been able to find information on the when the serial numbers for the s period represent for what year or month produced etc.
Ultimately it doesnt matter as im not looking to sell it. It is/was my fathers and i have it now for pigeon control. It hasnt been working well for some time so i wanted to find parts to try to fix it. I took it apart today and was able to fine the plunger is worn and one of the two main springs broken. I managed to find parts for it i hope that will work and they are on their way.
Id still be interested in dating it for personal knowledge though.
Thanks for any info given, its not easy finding much on this so far.