GenDryBat Earphone Battery Tester
This GenDryBat Earphone Battery Tester was used to test the 3-volt
batteries used in early carbon hearing aids. The name GenDryBat was a
trade name of the General Dry Battery Company, while "Earphone" was the
old name for what we now call "hearing aids". This meter dates to around
1930 or so.
The pin at 7 o'clock is the positive pin, while the screw post at 5
o'clock is the negative terminal. Typically a probe on a short wire was
attached to this terminal.
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