Children, children, stop playing with your toys. . . In the late 60's only a few weenies dove with the airlines type of CO2 inflated "chokers". "Real" divers didn't waste time with "dangerous" toys. You planned your depth, adjusted your weight belt as needed and swam down to the depth you were spending your tank on. If you went shallower, you picked up a rock.
General opinion at that time, was if you snagged the CO2 button, it would rapidly force you to the top and rupture your lungs. I free dove to 40 feet and watched the tiny bubble form in the vest. . . as I went up it expanded until at about 10 feet it finally had some lift to slowly bring me up.
The French created a bag type horse collar fitted with it's own air tank. Their idea was inflate the vest in an emergency. . . then breathe that air out of the bag. The Underwater Society of America required an inflatable vest for all competitors in the 70's, and I knew a lot of divers who wouldn't wear such a dangerous device.
In the early 70's I wore a horse collar that you manually inflated, only when I dove with students. To give the horsecollar it's due. . . It was low tech, but worked well underwater. Later vests, back inflates and Back Plate and wings just do the same job, at a much much higher cost.