What is this knob from kick panel?

[amg5872]

Hi can anyone tell me what this knob controlled? It was on the steering column kick panel to the right of the steering wheel. 73 Bavaria. Thanks.

 

[OCCoupe]

Not OEM.

 

[jefftepper]

My guess is that it is a fader knob for front and aftermarket rear radio speakers

 

[amg5872]

Makes sense. Thank you both.