dating goodyear NDCCs

[wtb853]

I recently purchased (17) 7.00 X 16 NDCCs (11 Goodyears, 4 Coopers, 1 Mohawk, and 1 Kelly Springfield) mounted on M151 rims. They have all seen some use but are in decent condititon. I have only found evidence of cracking or rot on 3 of the 17.

My questions center around the Goodyears. The sidewalls are very similar to the photos shown in the upper left on page 120 of Ryan's book. All the goodyears have "Military OZ" on the sidewall. I would like to find out the approximate age of the tires if possible. My understanding is that there is a date code system for civilian tires of that era and that it has changed several times since. I haven't found any clearly marked years as shown on the sidewalls in Ryan's book.

Is there a date code on the military goodyears? Can you narrow down dates by different features on the sidewalls? (i.e. "X" feature means after 19XX, buy "Y" feature means before 19XX)

I found an old post of Wes's stating "the military moved away from the NDCC tread by the mid 70s". Coupling this with the fact that the tires are mounted on M151 rims, I assume these tires date from the 60s or early 70s, but you know what they say about ASSuming things.
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1951 M38 (MC25486)