This is a used 1965 Ford Mustang Radio Rear Speaker Fader Control Switch with Knob and Wiring Harness. This would have been used for cars that had the optional rear window speaker.

The knob moves without any issues. The wires are still marked from when I pulled this out of my car back in 1997. (Front Speaker, Rear Speaker, Fader Control, To Radio Speakers Connect)

This part has not been tested; this part is close to 60 years old.

Hard to find original part.