I was not a diver then, but my understanding was that there were essentially 2 certifications for what we now call recreational diving--diver and instructor.
Interestingly enough, an article I read some time ago said that in much early diver training, as long, expensive, and rigorous as it was, there was no requirement for OW dives. Once you finished your pool work, you were certified.
And on the other hand, what was true for some early training, as described by some who were certified back then, was not true of all experiences. As a boy, I was introduced to the world of scuba by watching my older cousin dive in New Jersey. I visited that family for a week at the Jersey shore every summer, and for a couple of years I watched him don his wet suit and get into the water with his tank and his spear gun. This was in the early 1960s. I recently visited him and asked him about his training. He said he bought his gear at a local sporting goods shop, the kind of general shop that sells baseball gloves, etc. As part of the package he purchased, the shop gave him a couple of lessons. That's it. He just kept returning to the shop every time he wanted a fill. He was never formally certified. He stopped diving shortly after that and never did it again.