Kind of unusual fix for this one: About three years ago,I got a call from am maintainance man at a state hospital.(He showed his ID-LOL) The windows in the patients rooms had small cam locks on them so they could only be raised so far. He had a tamper-proof screwdriver which he could easily take the lock off, but he was getting ready to work on about a hundred windows-so he wanted a key.
He didnt know who the mfgr of the windows and there were no stampings on it.
I tried every damn small cylinder blank I had. Then I went through a coffee can of old keys and found one that not only fit-but opened the lock.
It was one of the older GM's-1098L I think.
I made him a few copies and told him General Motors was the mfgr.
goma.