Zenith TV date and tube code discrepancy?

[drh4683]

I thought this was rather interesting to discuss as its something I've never seen before. We all like to determine the time of manufacture of our TV's or tubes via date codes. Here I find something that makes no sense at all. The TV in this example is the '69 zenith I picked up at the estates last weekend. There is a tag on back of the TV, which I took a photo of. Look at the date when the set was purchased, 1-25-69. Also, look inside the set, the cabinet was built 1-7-69. The set was still hot off the press when it was bought from what I can tell.
Now take a look at the 6KT8 in the photo, its date code is 69-13. ALL of the tubes in this set are dated 69-13, and a few others are dated 69-09, which is normal to see a few tubes with different date codes that are close to each other. These are. What I don't get is how can the TV have been bought before the tubes were made? Does this code for tube manufacture really represent the month they were made? Or does the tube code represent something completely different? 9th week would have been the 1st week of march, 13th week would have been 1st week of April. Something doesnt seem right, and these are original zenith tubes. Zenith tubes printed in red ink mean they were service/replacement tubes.