Hi
In your 2nd pic, the credit unit.
there shud be two of those stop posts, not just one.
usually, the games were set to hold no more than 15 credits, most were less.
and thats where that post comes in.
set your credit wheel to "0". look at where the stop post is, it shud be holdin a switch open.
now, manually advance the cred wheel 1 step. the switch shud close.
now, manually advance the credit wheel to about 5 credits, and look at the switch stack.
are any of the holes lining up close to the switch?
get it to line up close, then see what number the wheel is on.
put the stop in the gear, and test the credit wheel up/down, and watch the switch stack.
when you get it where you want it, tighten the post.