So I found out that it was MAD Magazine issue #202 that started my odd and naughty little fascination with tan-lines. It came out in October of 1978 so I was a delicate little eight year old boy, LOL. But even at that tender age, I still knew that something about a boy bottom intrigued me, I just didn't know or understand what that quite was yet. Oh well, here I am all these years later and tan-lines still do it for me, who knew, LOL.
Here is a look at the cover art without all the copy.