an obscure RF device of some sort?

[slburris]

From the junk box of the father of a colleague...

This looks like it has N connectors on each end, and the tube
can be adjusted in length.  What is it?  Some sort of
RF cavity filter?

Scott

[migsantiago]

It looks like a pneumatic piston.

[Time]

My guess is some kind of tubeable cavity meant for matching.

[sonicj]

im guessing a partial antenna tuner.

[Kiriakos-GR]

This is an home made Gamma match dipole .

The length of the fat tube , can tell the frequency that it was built for.

The construction look heavy ,  so it can handle about 2KW RF ,
looks to was serving for an  "point to point" transmitting  link .

The pipe that holds the " Antenna " ( missing from the picture ) , it should act as the negative pole of the dipole.

Still the permanent adjuster on the capacitor , look like that it was build more as an experimental , than an usable item .