I got this in a lot of tubes and other radio parts. I can't find any reference to it in any tube site or on Google. The only marking is "VAR A3944". I'm thinking it may not be a vacuum tube at all and maybe is a ballast or the like.

Could be a relay or crystal too. But most likely a tube

Try and open it up. If the bottom does not come off it's a tube. Could be almost anything.

Could even be a cold cathode rectifier like an 0Z4.

They usually have a glass bulb inside the aluminum envelope.

-Steve

That was my first thought, but then I thought I'd give the forum at try.

If it's aluminum, no doubt has something inside that can be removed. I've never seen aluminum used on a sealed tube, too much expansion/contraction.

Well, curiosity got the best of me. I opened it up and this is what I found. I'm not well versed in diode identification. Would that be a 1n34? Anyway, there are four pairs in there. Still not sure what it was used for though.

Possibly a plug-in gate for an early computer? Who knows.. maybe even someone used the can for their own experimental doodad.

Var
Varactor diodes?

Ring modulator module.

Hmmm, nothing like that in my Ring Doorbell.

Trace out the circuitry, and post what you have. That sure looks like a 1N34 diode.

Looks to me like you have, some resistors, some nice crystal diodes for crystal radios and an octal socket for building a tube adapter or something.

Well, I was hoping there would be a flux capacitor in there. Here's the schematic, a little crude ,but it'll do. That's the bottom view of the "tube".

Aren't diodes used to block the reverse EMF when relay contacts open. I don't recall them being in parallel with resistors when used that way, but could it be?

viewtopic.php?f=19&t=356238

My version.

Frank

Well, so it wasn't a one-off or homebrew thing.

I wonder if it was made for some sort of military compressor or modulator as a plug in device to improve existing equipment?
There's this schematic posted EDIT (above, guess my in-line messed up) from a '46 compressor/expander I want to build written by a Sylvania Electric engineer in Radio News
that has a similar arrangement.