This may have been posted on, but I can't remember. I have read that code first required GFCI receptacles outdoors in 1973 and in baths in 1975.
I also read that the first GFCI receptacle was invented by Pass & Seymour in 1971, Leviton had one in 1972.
This is interesting to me, because I have never seen them used this early. My house was built in 1976 and has no GFCI breakers or outlets anywhere. About the earliest I had seen them used was in a relative's 1978 house. It had Square D GFCI breakers on two circuits.
I suppose our local code did not require them until about 1978, hence we never saw them until then.
Has anyone seen any from early-mid 70s homes? What did the first GFCI recepts look like anyway? The oldest I have are early 80s.