I found this guy in a lot of parts. It's a coil inside of a GT envelope octal tube. Unsure whether it's actually vacuum or not, but the leads go through the glass, so I'm assuming it probably is.

The only markings are "1212893", and there are two large "O" symbols on either side of the number about 1/4" away on either side.

What's this and what was it for?

maybe some military part?

Most likely to stabilize the coil. Humidity won't have an effect on the coil sealed in glass, less drifting.

I like that, I've been winding my coils on the outside of the envelope, what do I know...

Tom

Perhaps it is used in a crystal oven.

Well, one advantage for sure is that it would be easy to plug in a replacement.

Oscillator coil for 1939 Chevrolet auto radio. Maybe used in 1940 also.

Neat. I can def see the advantages of having the coil in a tube like that for a harsher application where it might be subject to temperature, vibration and humidity way more than a home radio would.

That makes two of us fortunate enough to have one.


In a triode (or a vacuum-selaled coil) no one can hear you scream.
Sorry, I just got wound up.

I have seen those before. They were used as a trigger coil for a camera flash unit.

From an old timer give MAG the brass ring. That is a Delco oscillator coil that was used in GM auto readios '37-'40. Unlike later auto radios that utilized permeability tuning the early car radios used a tuning capacitor making it necessary to have a local oscillator coil which was a "plug-in". Some of the older Buick and Packard radios of this era had two tuned RF stages and utilized things such as a "running board" and "trunk lid" antenna. I realize I have dated myself.
Tom.