Mystery object

[roadster]

With the above Triplett came this mystery object; approximately three inches diameter. The indicator is a magnetic compass graduated +/- 90degrees. There are three wires attached and there is another hole in the wooden body so there may have been a fourth. The compass needle always points to zero on the dial so there is some ferrous material inside the unit. Any ideas what its function may have been?
Rod

[Craig]

Phase angle meter?

[roadster]

Thanks Craig. In all the years that I have been working with phase angle meters or more correctly, in my case, power factor meters I have never seen a moving magnet type, but this could be simply to indicate lagging or leading without any accuracy. Initially my feeling about this object is that it was not meant to be functional and is just a prop but the fact that the dial is marked +/-90 deg. makes me think that is did have a measurement function. I will do a resistance measurement across the leads and if promising then try to remove the compass to investigate further.

[ppppenguin]

I wonder if we're being fooled by the 90 markings. It doesn't have to be angle; it could be voltage or current. So a centre zero ammeter might be plausible though 90A is far too much for that wire. 90mA? Or 90V if there's suitable resistance? If the coil still has continuity then easy enough to apply a voltage and see. The wires are of an old fashioned type,probably no later than 1930s, as is the little connector on the end of one of them.

If it's fairly sensitive it could be a crude galvanometer for measuring bridge balance etc.