This thread got me to thinking about a "Derringer" I bought many years ago at a pawn shop. It has a lock marked "Derringer" and "Philadelphia" with some engraving, but is otherwise very plain. The barrel is very thick and marked "Jukar" and "Spain". I am thinking CVA or pre-CVA? They sold it cheap because the hammer dropped vary slowly and no one wanted to buy it. I took it home and backed the lock screw off a half a turn and it worked fine. Screw was hitting the hammer. It is about .46 cal. so can use a ball made for a revolver. Not a pretty gun, but it is what it is. Don't think I have ever fired it myself.