As a kid I had very few issues of Famous Monsters simply because I was much more interested in the black & white 'adult' level comic magazines like Creepy and Eerie. I only had so much cash and the allure of dark deeds and possible breasts almost always trumped monsters. But of the few issues of FM that I did see I remember clearly my fascination with the ads in the back pages. Such wonders!
But if I had ever seen THIS ad I think must have blanked it out to retain my sanity!