Interestingly we needed have bothered applying it to most of the Gottlieb SS machines as they just never made the sort of money the Bally/Williams machines did (sorry guys that have G machines - it's a fact that they were pretty crap games as a rule - I thought so at the time and still do). The operator I worked for used to buy ALL new pins and generally several of each title. The Gottliebs never made him any money...........

Perhaps due more to their lack of reliability 

Early system 1 Gottliebs were just like early Williams, Bally and Stern games as far as essentially being EM gameplay, but with SS electronics.