There are 2 systems for numbering Zenith chassii. The old
system started with the tube count just like the radio days.
The first color was a 29JC20. 29 tubes, J=model year C=color ?
20 would change if there were different chassii. If one
were not changed the next year it would just have the letter
changed example 29KC20. Some times there is a letter at
the end. This is for minor changes & factory UHF I believe.
In the B line things started changing example 19EC45.
19", E model year, chassis. Same thing next year but 19FC45.
Model years are involved so here is a list best I remember it.
A, B, C, D, E, F, G, H, J, K, L, M, N, Y, Z then back to A........
Some letters were used only on big store sets, as I remember
S & SS, T&ST, V& SV.
Examples K1960W K line, 19", mid to high level, walnut finish
K1960P Same but pecan finish.
SK1961W same as above with remote, walnut.
Older sets used a "wrong" screen size ex. D4025W 40
means 19". This changed starting in H line to real sizes.
The second pair of numbers is the feature level. An
F4001L was a stripped carry over hybrid. An SM1971P a
high level TOTL set.
BTW there are exceptions & this is from a foggy memory !!
Need more ? Just ask.......
73 Zeno
LFOD !