A quick history of the ring-pull...
American Ermal Fraze patented an idea for a drinks can with a tear-strip in 1963 but his rectangular tab was difficult to grip.
In 1965, Omar Brown and Don Peters designed a ring to pull away the tear-strip and the ring-pull was born.
In 1975, Brown and Fraze patented the modern, "push-in" ring-pull, which did away with the sharp litter the original design had created.
I believe that in the UK the transition to the modern style of ring-pull didn't occur until the latter half of the 80s, with
this site claiming it was as late as 1989.