Really cool restore, you're doing a great job!
About those coil stops. The reason they have that weird profile with the ring in the middle, etc. is because on EM games the coils are run by AC power instead of DC power and the copper in the coil stop makes the coil not 'buzz' when the plunger is pulled all the way in, up against the coil stop. I'm not positive if they were originally flat, because I've never seen any that weren't at least 35 years old!