Where can I find suitable tubes for early video technology with tubes?

For early video technology with tubes, suitable tubes are mainly sought for preservation and restoration. On the private or semi-professional side, this includes devices such as the Philips EL3400, and in the studio / broadcast sector early systems such as Ampex VR-1000 or RCA TR-22. For the Philips EL3400, types including ECC89, ECF80, EM87, ECC85, ECC88, ECC83, EL95, EF184 and ECL84 are documented. For the studio machines mentioned, I was able to find reliable device sources quickly, but not a clearly readable complete tube list; therefore, I would prefer to mention only the devices in the FAQ. Anyone who needs the right tube for early video technology will find many of these types at BTB for the exact respective application.