I heard drug testing for the military didn't start until 1981. I don't think the technology was that all common in the early seventies.
they did implement some sort of drug testing in 1972 or 1973, at least that's what I read from other posts. but the drug testing was not part of an annual physical.
What I heard was that drug testing as a part of the physical did not begin until 1981. There might have been some before that time, but only if there was a suspicion that drug use was a problem.