I cannot be entirely sure, but I think that it was around 1990, that I saw the first
safety-shuttered outlets.
Maybe Old Appy has a better idea?.
But one thing is for sure, if they actually had safety-shutters in plug-in multi power boards, it would have saved the life of an infant over here,a couple of years ago, the child stuck an Auto key into the Phase aperture, this type of power board (like most of them these days) was imported from
China.