In older airplanes, locks are made of inexpensive pot metal and with a limited number of tumbler combinations, they're both easily pickable and openable by hundreds of keys floating around in the world at large.
As a last resort, buy a nut splitter if the nut seizes up completely, as corroded "pot metal" ones often do, you'll have to use a nut splitter to break it off (photo left).
The promotional car models were distributed by car dealers during the 1950s and '60s; in Don's collection are examples made of heavy plastic, pot metal and die-cast iron.
The longer sight radius was a little more difficult to hold steady since it emphasized your tiniest movement, but also forced you to concentrate on your sights and stay in the "zone." There have been many copies of the great Bo-Mar constructed from aluminum, castings, pot metal and MIM, but none ever matched the quality, precision and function of the great Bo-Mar BMCS (Bo-Mar Competition Sight) adjustable rear sight.