70s helmets were almost all "3/4" or open face helmets, in lots of metal flake colours. Usually came with a little visor thing (useless) and flat or bubble face shields were common. I mostly wore goggles though.
I bought a Bell once - before I knew how to tell if one fit - and I called it 'The Vise".
The only full face helmet I recall from back then was the Bell Star. I guess it was more protective but it was a car racing helmet with a tiny opening, so you had almost zero peripheral vision and had to turn your head like an owl to see behind at all. I never had one of those and only saw a very few bike riders use them.
Helmets have gotten incredibly better. My first had no padding, and a bunch of straps inside for the head like a hard hat has. Lucky I never tested it in action.
Shoei has been the best fit for my head. I've had several full face ones, I try other brands when I'm ready for a new lid but none fit as comfortably yet snug.
I have a couple of open face (old) helmets I occasionally for running out to the store on hot days, just within a few blocks of home on 40km/h streets. Feels weird. But going into any place without a mask on is going to feel weird as well.
