this is what is called a buzz box. If you have seen one please disregaurd. It is a buzzer - battery - 2 leads. It works just like the light but to me is easier because you don't have to look at the light and the points back and forth. You just hook it up and rotate the flywheel around while looking at the mark on the stator plate and when the buzzer quits your mark sound be on the F line (for stock timing) if not adjust points and try again.
One lead to the point wire out of the
Engine (disconnect from Coil wire)
the other lead to ground.
OMO