NARVA Glass envelope cristals suggestions
 

Hi everyone,

I have recently accquired some old glass envelope
cristals, similar in shape to a tube, with a 7 pin base. Pins are gold plated.

They are manufactured by NARVA.
There are following frequencies printed on tubes:
108.630kHz
307.95kHz
556.04kHz
307.95kHz

They look like they are in good condition with
clear printings in yellow, but I have no possibility to test them. No boxes.

If somebody has an idea what to do with them,
or maybe wants to make any use of them please drop me a line.

Thanks

Lukas