[rotorwrench]

That big C shaped ring is another give away for an original type. I've not seen it in the reproductions.

The other posts are correct about the voltage change. Bad batteries and wiring in poor condition or loose connection can cause higher voltage depending on how high the 3rd brush is set. Ohm's law pretty well accounts for higher voltage if current output is high. The resistance, amperage, and voltage all affect each other according to Ohm's Law.