The pin that is limiting it is likely removable/adjustable. You can unscrew it and put it in a different position. Should be different holes in the credit gear for different max credit options.

That is the credit unit which keeps track of the earned or remaining credits. There are limit switches to keep the credits in a range of zero to some operator settable upper limit. More info at:

https://www.pinwiki.com/wiki/index.php?title=EM_Repair#Williams_Credit_Unit_Examples

/Mark

Yes, it IS a credit counter. There are historical reasons why everything related to credits was unlabeled in the EM era. The operator of the game could adjust the upper limit; one operator in my part of New England was notorious for setting the Williams games, even the four-player ones, so that the credit wheel would go no higher than 8!

With the power off, you can manually actuate each of the solenoids to see which is add and which is subtract. Then look sideways at the main gear and you will see posts sticking out that open some switches at the zero position and some other switch at the maximum position. The latter post can be screwed into one of several threaded holes to set the limit.
.................David Marston

The credit unit has to combine credits from all sources, paid and earned. Paid usually only applies to the 25c slot in American games, but other countries could have two slots that take two different high-value coins. Earned replays would be on score, special, or match.

Free play is usually accomplished by defeating the zero-position switch on the replay counter. The switch blades might always be touching, or a wire could connect the blades electrically.
.................David Marston