Questions on 1958 COLOR Raytheon C-21C1-M Television

[SpaceAge]

I would agree with what reeferman is saying, most likely you have a tester issue. If you believe it gave accurate readings for the Zenith, I would run with the assumption that you have a good CRT and disregard the short light. Someone from Chicago may be able to help you with another tester.

This is the Early Television Museum’s database of surviving sets, yours is now the third of that model. Contact them and they will add yours.
https://www.earlytelevision.org/color_database.html

Congrats on the find.