The only number on mine is 512-4. When I get the new switch, I’m going to try getting a repro to work. The recess for the steering wheel compression spring is on the opposite side, the post that holds the horn contact is too long, and the canceling tabs are in the wrong position. But I think it might just work with some simple modifications. The exact version I have doesn’t seem to be available. My original may also still work if I can use enough epoxy to keep it from falling apart.