To my knowledge, Zenith was the only manufacturer which used the 6JH8 "sheet-beam" demodulator tubes; I can remember an old TV commercial from the early 60s boasting of "Zenith's patented color demodulator".

I always thought that the '62-'72 Zeniths had better color than the RCA sets; if you watched a football game on a Zenith, the field was really green instead of a blueish-green.

I worked for a Zenith dealer 25 years ago, and worked on most of their tube color sets. Charlie's picture tube is a rebuilt tube; if it is a Zenith it was probably installed by a Zenith service dealer. The 29JC20 and the later tube Zeniths were much easier to work on than some of the other makes.