oops, my bad. I put a 3-way into a Custom 24 , replacing the 5-way (which I do not like). I had to enlarge. You won't.
It's a five click rotary knob. I call it a switch. Eitehr way, you can get them from PRS.
Matchless and Bad Cat use something similar on their amps. Essentially a 5 position tone selector.