That is a ported vacuum switch. $15 to $20 new.
IIRC the 2 nipple one ties in with the EFE valve keeping it closed when cold and opens when warm.
Or the 3 nipple one ties in with the EFE, and Y's in with the EGR and Charcoal Canister to pull fumes when the engine is warm
Look it up based on the year/engine of your car, the '60's engines never used them.
If it's not hooked up/controling anything, get a pipe plug & call it a day.
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