Even small gunmakers have surprisingly good records. Giriffin & Howe, Dietrich Apel, and lots of smaller ones have been able to go right to their records. Even small German gun makers are documented in books. I found a beautiful engraved rifle made in a little town in Czechoslovakia in the 1970s. I found a little webisite for them, sent an e-mail, and the semi-retired gunsmith answered. He had built it for Communist potentate. I was able to trace a shotgun built in Germany by a man who only built a few hundred of them before WWII broke out.