The first pdf (on page 3) gives a May 1962 issue date. They all appear to be early 60s for the most part. Certainly all pre-1968 since they are all English measure. But, probably all are early 60s would be my guess.

Earl

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Earl L. Cagle, Jr.
NAR# 29523
TRA# 962
SAM# 73
Owner/Producer
Point 39 Productions

Rocket-Brained Since 1970