AMI used part numbers starting with S for standard or C for custom. Their 1979 catalog shows an S2567, but that's a 14-pin chip for an electronic organ.

I'm guessing it's an S2000 MCU, with C2567 representing the custom ROM. If we could get a picture of the solder side of the PCB, we could tell if that's correct. has pics of 3 different PCBs. I'll ask if he could scan the solder sides, too.