[pcravero]

I had to see the resonator and I found a surprise. A previous owner has replaced the original innards with a 10'000 kc/s XTAL oscillator, so he got an ovenised XO. Well, I might try crystal grinding to put it on 30m HAM band. I did measure once a 10 MHz output, but discarded it as noise and never appeared again in later tests, probably due to loose contacts inside the tube.

The curiosity remains on which device used a 4 kc OXO in 1957.

Thanks for reading and contributing!