I have always been fascinated with the mechanics of locks, key and rotation. I have never tried much with keyed locks but I have spent a lot of time to rotation locks. You can feel the mechanisms inside of the rotation locks if you work them slowly enough, then try a feel out the numbers needed.
Here is an interview with a real professional.
I still play with a few locks around the house, they are kinda like a puzzle to play with while you are waiting for something.