My '47 clock must be different .... has one wire and no points. There are at least two manufacturer's - I have a "Westclox" of LaSalle Ill. stamped "Ford" in script; and there's also a ford clock by "George W. Borg" of Chicago Ill.
In the Westclox unit, a small spring-metal tension blade on a sub-shaft engages and puts rotational pressure on a main gear and shaft causing the clock to ultimately tick. When the blade's pressure decreases to a certain point, an arm on the back side of it grounds-out (no points) activating the twin coils, which rotate a swinging bar, that re-winds the mechanizum. Whatever ... the operation is simple and appears not to be subject to effects of Pos/Neg ground systems. Dan