I originally blogged this in a 26 January 2014 post at Infernal Wonders, but my source for this was this post at the aptly-named Bondage Blog. The knowledgeable proprietor over there, Rope Guy, included this commentary:

’m not sure exactly what the eerie ray the bug-eyed monsters in the tentacle-suits are pointing at this poor girl’s bottom is supposed to be doing to it. But judging by the rapt attention of the audience, it must be something rather entertaining!

Along with this attribution:

Art is a detail from the cover of an old Marvel Science Stories.