R.H. wrote:


You're correct in that it's not electrical, there is no contact on the
bottom, nor are there any coils inside. I've shown it to a couple of
electrical engineers and we all agreed that it's some type of
vibration indicator, as was mentioned by Andrew, but we could only
guess at it's exact use.

There is no company name or patent date on it, just some numbers on
the back that yielded nothing in a search. It does fit into a light
socket, and note that the back plate is shaped like a light bulb, a
couple possible answers that I've heard:


-Used by a bulb manufacturer to test the strength of filaments
-Used to test the amount of vibration that a bulb would have to
endure in a particular machine, such as a large projector


These are just guesses but I think they're on the right track.


I once heard of a curious situation on the shake-down cruise of a heavy
cruiser. When the 10" guns fired, every light bulb in a certain section of
the ship shattered!

Maybe this gizmo is a Naval Bulb Vibration Test Instrument, Model 44-A2/2.