[drh4683]

After checking a few sets, I believe its purly coincidental that the numbers appear close to the approximate assembly year of the TV. I checked a '66 Zenith roundie I have, the back was written "Purchased 9-1-66" and the code reads 68G16.

I have a '69 Zenith, the code is 16A14, its a metal cabinet color set, the date stamp inside the set indicates 1-7-69 and the back of the set was written "Installed 1-25-69", incidently that set was hot off the line when it was bought!

As of now, the best way to determine assembly is by original tubes, or if you're lucky, sometimes they have the actual date stamp on the inside of the cabinet. Another way is the filter cans sometimes have date codes as does the 3.58 crystal. Later zeniths have the actual month and day date printed on the delay line.