The #21a, 21b, and later 22 were options installed at the factory or available separately for many years. Pre Great war and post. Later guns tend to have a #22.
This is the one I want. BSA #12 sight. Available on Improved Model D's. Rare. Fits into a milled place on the trigger block. Could be ordered on the rifle or you could send your trigger block to BSA.
45 inch guns with a later skirted piston shoot nice. Later IMD's and post war long Standards. All .22's. No twang. Just a jolt when fired. Get one. BSA made big numbers of the 1919-20's. Keep your eye out for one.
i asume they are spring powered guns?are the accurate do they shoot hard?very cool looking i have never seen one.
very cool i have a newer diana break barrel and i find its acuracy very poor but i have been reading other people find spring guns accurate? not sure why mine isnti will have to keep an eye open for one of the those BSA mostly just ecause i love old things.