Points Distributor - What's This???

Thing is "they changed" that stuff about every year. The vacuum pot is indeed solenoid retarded, so yeh, I'd guess an associated relay

The ones I'm familiar with had a contact on the idle screw, some used an idle solenoid, so that when the thing was down on the idle stop, it grounded and engaged the retard solenoid. Unless you are doing a "restore correct" or need it for state law..........you don't want any of that...........