REM 3200
US Veteran
Call a locksmith. That's what they are there for. 

Call the IRS and tell them you think you lost a dime in there that you didn't report.
Didn't try that but I did give it the "Fonzie" slap.![]()
Jinglebob, Try some forceps. First spray some lube into the lock. If it hasn't been used for a while, dirt and oxidation can and will cause it to turn hard.
The broken part of the key needs to be turned so it clears the keyway on the way out.
I would not drill just yet or use any kind of glue. Seen many times where people use glue and it causes the lock to become unusable. Besides, glue won't work anyway.
Drilling is a last resort because the lock will be ruined. But if the key doesn't come out you may not have any alternative. And finding a replacement lock won't be easy.
If the forceps don't work let me know. Hopefully it does work cause calling a locksmith out can be expensive providing you find one that knows how to handle this situation. I hate working on these in the field.![]()
The use of forceps is a good idea. I'll give it a try. I hesitate to call a locksmith because the closest is twenty miles away in Sulphur Springs, Texas. The service call could cost more than the cabinet is worth. As you state, a matching replacement lock may be hard to find. The cabinet was made in the early 1980s.