Insulator for a rotary potentiometer. Most old car light switches had them for the dash light circuit. I've seen them on variable speed wiper motor switches also, along with other applications. Usually, the automotive applications weren't quite that thick however, so, it might be for some other industrial use.
Yes!! I agree. (Nice ID, CudaMark!)

I couldn't quite put my finger on it, but I think CudaMark has nailed it. (I'm an electrical engineer.)
This does indeed look like a ceramic insulator for an embedded coil of some sort.
Automotive applications would include panel light dimmers or air conditioner controls.
It could be either a rheostat or a potentiometer. (My guess is rheostat, which is maybe best explained as a two-wire "potentiometer" - to keep it simple.)
You would need to see the rest of the device (missing) in order to determine the exact circuit.
It might not be automotive, though - as CudaMark suggests.
It could also be part of a heater element. The ceramic would hold the wire coil, which when powered-up, would glow a nice orange color.
A final possibility is it could just be a ceramic form for a high power wirewound resistor.
Same basic principle though: a ceramic form to hold heater wire.