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[Linked Image from 3.bp.blogspot.com]

A broader Marvel Comics subscription ad for their entire line of comics.
From MARVEL TEAM-UP 68, April 1978, and other Marvel issues the same month.
https://readcomiconline.li/Comic/John-Carter-Warlord-of-Mars/Issue-11?id=83627
https://readcomiconline.li/Comic/John-Carter-Warlord-of-Mars/Issue-3?id=83669

It appears to be images from various Marvel comics, pulled and pasted in a collage of art panels in this ad.
That I can recognize, Howard the Duck by Brunner, Conan by Gil Kane, and Captain Marvel by Jim Starlin.
It has a similar look to several New York Comic Con posters of the period, by John Buscema and others.