I did my first scuba dive in 1959, using borrowed equipment, a Nemrod double hose regulator and a US Divers tank and Bac-Pac. I had my own fins, mask and snorkel. I was 16, and had been free diving and snorkeling for almost 10 years at that point. I remember that I began buying equipment from Koseff's on New Jersey's Long Beach Island the following year, piece by piece. I dived occasionally, but not as much as I did years later. Solo diving at night in rocky inlets for lobster comprised 90% of my dives.
There were no SPGs, of course. J valves were what we relied on. There were no SPGs when I entered the service a few years later. I'm not sure when they became available. I spent a long time in Jamaica after I left the military. No SPGs were available there either, though everything else any sane human might desire was. It was in Jamaica that I really began diving seriously, in 1970.
There were no SPGs that I knew of when I eventually got certified in 1972, but when they became available a few years later (my memory regarding exact years is a little misty) it was as if all the problems of the universe had been solved. I bought one immediately, a Scubapro with a black face that I used for the next decade.
I started doing some wreck diving, and returned to the Caribbean as often as possible. It was a paradise even then. It is not a paradise anymore, but I still return several times each year, always hoping to catch a glimpse of what used to be. Like visiting an old girlfriend.
When I saw my first SPG I decided that now any moron could scuba dive. I was right.