Firearms which are certified by the curator of a municipal, State, or Federal museum which exhibits firearms to be curios or relics of museum interest; and
With anything over 50 years old already C&R, it seems to me that most of the guns that would fit that category are C&R now. Some rare guns are not, but it only takes a letter to BATFE to have them put on the list; collectors do it all the time. That is where those "50 pieces made on special order for the King of Botchedupland and issued to palace guards..." descriptions come from.
