Adco has no connection to your shotgun. They import semi-automatic shotguns made in Turkey. Diamond Arms Co was a trade name used by Shapleigh Hardware of St Louis, MO, on shotguns imported from Belgium c. 1880-WWI or made by Stevens and Iver Johnson from about 1900-1940. A single shot with serial numbers is most likely an Iver Johnson Champion.
Your local gunsmith may be able to clarify whether or not Winchester actually manufactured that shotgun for Sears.
The diamond 12 says it is a 12 gauge and the crowned ELG that it was manufactured in Belgium after 1893.
Manufactured by Davenport. firstname.lastname@example.org
Whats it worth?
Your shotgun was manufactured in 1947.
Actually the shotgun uses 16 gauge shells i have the same shotgun
1956 This shotgun WA manufactured in 1956