I bought this car used, and came with a whole load of things installed. Just came across it yesterday. And I don't have a clue. Otherwise I would not have asked it. Wouldn't I. Somebody in Germany made this adaptation I guess, that's where I bought it.
Howdy! Yup, I have a similar setup on some machines at work. For me, I can slide the metal band up or down to control how fast a large magnetic clutch takes a roll of paper from zero up to about 200 rpm. You'll probably have to trace some of those wires to see what they connect to. JohnI agree that it is some kind of adjustable resistor