touch tactile button
You're probably right...

It's very likely a capacitive keyswitch body. The 4 pins are DC power (2x) and a floating output (typically the collector and emitter of an NPN). The sponge (which isn't graphite) conducts the electric field lines down to the electrode (plate) in the well of keyswitch body.

This particular part must be old or custom as I couldn't find anything like it in that formfactor. The closest ones I found are configured like this:



Maybe someone else will have better luck?