White Electrical Instruments Ohm Meter (1930s)

I bought this lovely old ohmmeter at a boot sale in England. Manufactured by the White Electrical Instruments Company of London, it has a solid walnut case with dovetailed joints.

Lacking the proper battery, I haven't tried to use it. There's no reason to take it apart, either, since I'll find nothing but a few wires connecting the meter, battery, and other components.

The test terminals are on the right side of the walnut case, along with a momentary-contact switch that you depress to make a test. On the other side is a big round potentiometer knob that lets you compensate for the battery's decreasing voltage as it discharges over time.

I'm guessing that this meter was built in the 1930s, or possibly earlier. If anyone has more information, feel free to contact me via email.