I attended twice. If I recall correctly, the first time was in 1983, then in 1985. The first time I attended, the school was well-established so start time in the late 70s seems about right.
The school was at the Ruger facility in Newport, New Hampshire. The first time I attended, I was there two weeks. The first session was only on the security six. At the time, Ruger was marketing heavily to police departments to use the security six instead of the Smith & Wesson. A federal study and come out that was critical of Smith & Wesson and favored Ruger. We were all given a very nice spare parts kit for the security six revolvers. The second week was on the mini 14. Likewise, Ruger was marketing this carbine to police departments at the time.
We got a very nice factory tour and saw all phases of the manufacture done at Newport, New Hampshire. This includes casting, stock making, assembly and test firing. Ruger's staff took us to lunch a couple of times, and there was a very nice closing dinner. At least one of the two times I was there, we were taken out one afternoon for range shooting. This was at Bill Ruger senior's farm. I never got to see or meet Mr. Ruger and he was not at the farm we were there. I did look in the garage and see one of his custom cars (did he call it a Blackhawk?)
I attended again a couple of years later, in 1985 I think. By that time, P-85 had just been announced and we got to handle them, but they were not available to test fire.
As part of attending the Armorer school program, we were permitted to buy one firearm at 62% of retail, excluding the AC-556. Upon completion, we were given a certificate, armorers school pin and patch.
If I recall correctly, the head instructor when I was there was a fellow named Mike Miller. The second time I went, Ed "C. E." Harris worked at Ruger and was around a lot.
If I recall other details, I will post them. Ruger did a first-class job with the Armorers school. They were competing with Smith & Wesson who also did a fine job.