I would need a more detailed description or photos to be sure, but I suspect you have a "Zulu" shotgun. These were made in the late 1800's by removing the breech of old military muzzle loading percussion military arms and fitting them with various types of breech loading mechanisms as cheap shotguns. The B in a shield is probably a European proof mark.
when was the carolina arms 16 gauge single barrel shotgun made
Best lef to a gunsmith
50-125 USD
What isthe value of a Stevens double barrel hammer type 12 gauge shotgun Model 235 and when was it made?
nitro hunter shotgun single barrel with exposed hammer stamped belknap hdwre and mfg serial 5516
Go to Google, select IMAGES from the toolbar, and for search term enter Iver Johnson double hammer shotgun.
25-150 usd
You will need a professional appraisal
The 1894 was a side by side barrel the 1893 was the single shot
Seldom go beyond 150 USD
50-100 USD
Your Iver Johnson double barrel shotgun can be dated by the words hammer forged.This places production from 1936-1941.these were well made mass produced field grade shotguns of high quality.