Have you tired the internet?
Dozens of comapanies.
I would have to do some searching to verify this, but I don't believe Stevens ever made a shotgun using percussion caps.
Old gun catalogs, library, gun shows, gun shops, Blue Book of Gun Values, Standard Catalog of Firearms.
50-100 or so
This needs more information. Such a gun would be a percussion weapon, and possibly converted from a rifle, assuming 1846 as a mfr date. Get photos and post them on one of the antique firearm fora.
Never heard of the maker.
I just purchased the same shot gun with a bird head handle.
The percussion cap was first invented by the Scotsman Reverend A Forsythe in 1803. His main reason for developing the system was to provide instant ignition to aid in the hunting of game birds (Forsyth was an avid duck hunter). His first percussion arm was of course a shotgun. Although patented in 1803 the percussion cap was not utilised on military arms for another 30 years.
I can get information on a Stanley Arms shotgun from my brother. He is never wrong, either.
Not enough information.
Sorry- there is simply not enough information in your question to answer it. Which shotgun? Which spring?