Smaug Ichorfang wrote:
The more I look at 1338, I wonder if it is indeed aa metal-foil
electroscope. Typically these have very thin pieces of metal foil
suspended from a central conductor. The center piece in this looks way too
thick to be an electroscope. Does the center piece move; can it pivot from
side to side? Are the two terminals on the sides adjustable? Is it
possible this is a tilt switch of some sort?


(I hope this isn't a double post. There's server trouble.)

How about a line frequency monitor from a time when automated equipment
to keep a generator on frequency was not reliable.

The power-company supervisor keeps one of these near his desk or bed.
With its exposed terminals, it would probably be above head level.

The center element has the mass, length, and stiffness to resonate at
the desired frequency. It's connected to rectified voltage. The side
elements are connected to the two sides of the AC line. Sliding them in
or out adjusts the volume of the hum. For safety, maybe the knobs are
varnished wood and not metal.

If the device stops humming, the supervisor phones the power station to
adjust the generator's speed.