The Super-8 film format wasn’t introduced until 1965 and probably not commonly used until a few years later. Before that there was “regular” 8mm and 16mm for home movies.
I shot Super-8 video of my kids in the mid to late 1970s. Super-8 had not been public all that long. I suspect it was made public by Kodak around 1974 give or take a couple of years.
I was wrong. Evidently the Super-8 format was introduced to the public in ‘65. I thought it was merely developed then.
I still think it’s highly unlikely more than a very small group of people were using it until the mid ‘70s.
In the mid ‘70s they came up with a cartridge format, that become quite popular for a while.
http://motion.kodak.com/motion/Products/Production/Spotlight_on_Super_8/Super_8mm_History/index.htm