I bought an Oscilloquartz 3210 on Ebay a few years back. On collecting it, discovered it was one of three Racal portable frequency standards, with battery backup, in short racks. Made a cash offer for all three, which was accepted. On test, two worked and locked in tens of minutes from cold, bags of beam current. The third looked ok, but zero beam current. Did a bit of work, tracing signals etc, but unable to make it work. Sold and shipped it to a collector in Japan, to recover some of the outlay. Still have the other two, ion pump and vcxo on all the time, then tube powered up once a month or so to keep the circuits and caps ok. One will be for sale (or trade) at some point, but no rush. Compared to each other with a phase meter, zero detectable drift over days, but they are good enough to detect the sawtooth like drift of the lab gpsdo. The 3210 is an all analog design, so quite early, but iirc, uses a Frequency Electronics tube. Amazing accuracy and far more than I need for work done here, but they do scratch a time nuts itch and add to the frequency standard collection...