Some locksmiths have a large ring of keys. By trial and error they usually can find a key that matches the lock. Then using that key as a template, cut a new key. I don't know if it is universal, but on my '37 truck, the key code was stamped on the door handle barrel. But to get to it, the inside door panel had to be removed, and the handle removed from the door.
Thank you both for the response. I will try a few local locksmiths to see if any have the master key set. Some of my early GM keys will almost work so perhaps I might stumble across a working key at an auto flea market.
Loc: Bakersfield Ca.
here in my town there is a guy that has van and parks in a vacant lot and makes keys. Ive took my handle to him and made one on the spot the old fashion way. He puts a blank key in the lock and wiggles it back and forth so the teeth will make marks on it , then with a file he will cut it out by hand. Cost about $25
On my '37 Master Coupe I was able to remove the handle by removing a screw that you can see through a small access hole just next to the door latch. You have to turn the handle slightly to see the slotted head of the screw. Keep turning the handle as you remove the screw.
The numbers were stamped on the portion of the door handle inside the door. A local locksmith was able to make a key based on that code. He then rekeyed a replacement Electrolock cylinder to match.
So now I have one key for the door and ignition which is the way it came from the factory.
The handle I have is already off and was part of a package of parts I received. My main purpose in getting a key is to make it complete and perhaps more useful for a new owner. I do not see any numbers on the inner part but will take another look.