My Firepower, Sorcerer, Pinbot, and Earthshaker lockdown bars (systems 6 thru 11) all look exactly the same but don't seem to lock the same from machine to machine. I think it's just that the two locking tabs are bent slightly differently on each, perhaps due to the differences in playfield/glass angles; they should otherwise all be interchangeable.

I read somewhere that the same lockbar was used on all standard size cabinets from the early 70s EM machines through System 11.

-scott

Actually, I believe the same bar was used from 1965 through 1990 on standard width cabinets.