1952-59 Ford 56 Radio Question

I have the standard radio in my 56. The left shaft has a chrome tuner knob which I think is for b*** and treble that sits behind the main knob. It is keyed or slotted to fit on a br*** looking sleeve that turns when the chrome knob is turned. The right shaft has the same set up but it doesn't have the br*** looking sleeve but the knob is slotted and it just kind of sits there behind the main black knob.

Is the right shaft chrome knob suppose to tune something or is it not suppose to move? It is slotted like it should tune something but the br*** sleeve that it would fit over is not there. I'm wondering if I have the wrong chrome tuner knob and there should be one that isn't slotted that goes on the right shaft.

Any help would be appreciated.

Thanks

 

it has been years but I think the right one controlled front and rear speaker separation