There is a switch labeled reset pos. 100M unit. NC. During reset, the motor continues to run until the reset position is hit, then it opens. There are several switches which also feed into that circuit. Hard for me to see from the pic there.

The 100M unit reset coil engages with the slide switch - normally on Chicago Coin, there's a stack of two or three switches that the slide hits as it retracts. One of these engages the reset coil directly (T?) as well as the U relay/coil which is probably ball count reset.

Keep in mind that the switch, as drawn, may also be a rivet, just to be more confusing.