Let me see..
WMS, Bally, GTB, Stoner, MIdway, Genco, Nasco, United.
I think that's all.
Early Bally coils can be put into Midway and WMS shooter games and vice versa
WMS coils can be put into Segasa games
GTB are on their own.
Zaccaria are on their own.
SS Bally = early Stern.
Theory of mechanics is similar to all machines.. but then again, I don't have a machine past 1981.. later than that and it may be different
