I worked on a lot of old equipment, and it all had the same problem, it was unreliable, drifted like crazy and NEDED calibration to attain what are now considered mediocre specs. These days any voltmeter from a company like Fluke etc. that is ~1% accurate usually doesn't need calibration, we just do it because the standards say so. Get to 0.1% and you occassionally need calibration. Things sure have improved
The caption says there's a CRT in the upper right corner of the capacitance bridge panel in image 13, but is it really? I have a hunch it's just a little screen over the top of a 6E5 "magic eye" tube but I could be wrong, those were quite common on test equipment of that vintage and function. Basically it's a replacement for a meter when all you needed was an indication of an analog null condition, like showing that the bridge was properly in balance.
There's a few Russian companies that manufacture vacuum tubes, some even make them to order. A friend of mine wanted to make a valve amplifier that actually produced high quality audio and designed a valve that met hit criteria. He's using one of these companies to make it :-)
@prabhakar_deosthali, that may be the one thing that puts a company like IET out of business. Everyione who works there is an expert at his or her job and has been doing it for many years. When they reture, who will replace them?
There's another issue and that is because these people have a unique skill that's not necessarily transferable to other jobs. Thus, they have a job for life as long as the company stays in business, but there's little room for advancement or for changing jobs.