Like dlc, I mostly predated the rating system but there were certainly "adults only" films. When Bava's Black Sunday played in Corpus Christi, no kids were admitted. I was turned away from some "adult" comedy (I think it was the completely innocuous What a Way to Go!, because at age 10, I was too young for the ticket taker's comfort) at the Texan in Greenville. The rating system started right around the time I was too old to care. Going to see Barbarella, when I was 15, the film was rated M -- the R of its day -- but the theater didn't bother carding me. That was pretty much the way things went after that, even for the X-rated Clockwork Orange. Still. it was a relief to turn 17 and be beyond the whim of the boxoffice.

I let my sons watch R-rated films pretty much from the age they first showed an interest in seeing them, being of the school of thought that it's better to watch with them and talk about the movies because trying to keep kids away from "objectionable content" today is pretty much impossible without chaining them to a chair and taking away their computers. Upshot is that I've raised two film critics.