Re: Shotgun in the wall
It may be worth twenty bucks or so as a novelty, complete with story. But it was a cheaply made shotgun when it was new, and age probably hasn't improved it any. "Compressed steel" sounds like another name for Damascus or laminated steel, made up of spiral wound strips or hammer welded plates. I strongly recommend against firing it with ANY ammunition. I suspect, though, that this may be a case where the owner thinks anything old is valuable; if so, simply suggest he take it to any gun shop or antique store and get an estimate of his own.
One way to use a gun like that is to render it unusable, then display it in a shadow box as a decoration, with a card saying where and how it was found.