writes:

I think there is a piece missing from the device, it was like that when
I bought it.Looking at the inside of the tip of the device, there is a
round metal tube which has a bottom, a little philips head screw holds
the metal tube in place.
cuhulin

Possibly an Oudin or Tesla coil for checking vacuum systems and other
equipment with high voltage like:

http://www.electrotechnicproduct.com/

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