This 250KΩ volume potentiometer has a special P taper characteristic enlarging the effective zone of a rotation when volume adjusting.
The extra feature of this potentiometer is an adjustable parallel treble bleed circuit.
There are 3 jumper switches and in the OFF position there is just a basic capacitor acting on treble bleed control.
When all of the 3 jumper switches are ON position you have the maximum capacitance acting in the parallel treble bleed circuit.
The trimmer potentiometer is adjustable with a simple screw-driver which affects the resistance value of the treble bleed circuit.
The combination of jumper switches and setting of the trimmer offers almost infinite values of treble bleed impact on the volume control.