Looks like caulking, perhaps to reduce the vibration of a wire getting broken off?

John

Silicon caulk can be used as an electrical insulator after it has fully cured. Interesting location to use it.

I've got a Black Jack with similar looking stuff all over it. Never figured out why

Ops often did things to lessen service calls on location games. One local op years ago would unsolder every wire to every coil lug and put heat shrink tubing on the wire, solder it back on. Then heat the tubing.

Rarely had a wire break off service call.

This seems like an attempt at the same thing. Only easier and less time consuming.

LTG : )

It doesn’t cover the areas where the wires are soldered though.

I wonder if you peeled the caulk away you wouldn’t find that the plastic is cracked or broken and that’s reinforcing it.

The caulk/RTV/Silicone added as shown is to prevent the solenoid winding wire from breaking off near the power wire lugs/tabs. How many times have we all had to repair the thin one on the center lug on an early SS Bally flipper coil? Or just replace the coil?

I know an old operator who told me he had to do that on every solder connection on some of the earliest gottlieb system 1 games when they first came out since they kept coming apart on a regular basis.

Yeh, that looks like an operator squirted on some silicone caulking to prevent wire breakage service calls.