I would guess that these are exampes of "under the counter" items. There used to be a news stand at the corner of 12th & Main in Kansas City that you could buy what we now call pornography. I didn't, of course. Betty Page was a Pin Up Girl in the early 50's, and aside from her pin up pics she probably posed for pictures like these, which couldn't be shown to the general public, to enhance her income. There's a world of info on Google.