Probably the 20Y1C36
Tuner knob should be chrome T-shaped. Common step-up
layout for 3 yrs. Only transistors on main chassis would
have been for AFT IIRC. This was our first colored set. The
old man got it to watch the '67 Red Sox in the world series.
They can run forever. Ours had the bridge rects go under
warranty then I changed a few tubes over the years to perk
things up. CRT never went bad or had a cataract. Lost track
of it in the mid 80's, he wanted a cable ready set.
73 Zeno
LFOD !