today I found the source for the cover of Sexy World: in the Book "Pin Ups: A Modest History" (1972, reprinted 1996): the picture is from a Dec 1971 edition of Playboy Japan (unrelated to the US Playboy) and while the full version is more explicit, it's hard to see how it could be cropped to fit on a CD cover without losing the tits etc.
In the context of the book, full of 30s-50s glamour shots, 60s/70s cheesecake and long dead and forgotten Victorian seaside porn posers, the "Sexy World" cover looks strikingly exotic, more like a still from a cult Sci-fi film (hi-lit embryonic intimacy) than the faded smut that surrounds.
It seems even more mystiqueful being distanced from the known territory of pin-ups in space (Japan, the utter obscurity of the magazine) and time (1971 as distant culture past viewed from 1998, Dec. 1971 as portent of the future viewed from a book released in 1972)