This is a on off switch for a McIntosh 2120 stereo power amp. It is a snap switch of sorts built in a potentiometer case with the switch attached. The shaft is 25mm. Due to the fact that it closes a relay I don't think it has much current running through it.
I just can not seem to find anything to replace it. Both Digi-Key and Mouser say they don't have anything like it.