Best way to tell is by EIA numbers on the part.
EIA #'s are one to 4 place numbers with each mfg having a ##.
Example is #343 for Zenith. It can be any brand but if you see
#343 on the CRT you know Zenith built the CRT.
Other info you can find on parts is.
Week & year date codes, 4 places. example 4578 is 45th week, 1978.
OEM part ##'s.
MFG part ##'s .
Run ##'s
Values.
All can be useful ! AND fun
Now someone that has the list of EIA ##'s please post. I cant find it any more. I knew many but age is slowly eating away at my brain list !
73 Zeno
LFOD !