A couple of these have shown up. Dixie Gunworks had a 10ga like you describe with Bernard pattern damascus. Take the barrels off and turn them over. There should be some proof marks, most likely Belgian. You can look them up here:

http://damascus-barrels.com/bp.html

The proof marks will at least put near a date of manufacture. It does sound like a gun made for a hardware store or catalog house.

Pete

http://www.damascus-barrels.com/Movie.html