When Newton Comics published Unknown Worlds of Science Fiction #2 (cover-dated February 1976) they promised a "Free Color Poster Inside".
As it turns out they did not deliver a colour poster but they did provide this gorgeous black and white specimen (my apologies for the cropped scan):
This is a black and white print of a Buck Rogers illustration by Frank Frazetta which originally appeared on the cover of Famous Funnies #214, cover-dated November 1954:
I don't know how Newton came to use this image as a poster in this issue. I've spent a bit of time indexing the Newton and Yaffa issues of this title, and have unearthed a few interesting things which I will detail in due course, but I wanted to throw this one out now in case anyone can shed light on where this image may have been published - presumably by Marvel - in the mid-1970's.
I've looked at scans of all six issues of the U.S Unknown Worlds of Science Fiction series (which provide the material for the Newtion and Yaffa issues) but have not come across this Frazetta illustration. I haven't seen a copy of the Unknown Worlds of Science Fiction Giant Size Special, so it's possible that it appears there, but given it has a 1976 cover date, and the Newton Unknown Worlds of Science Fiction #2 is cover-dated February 1976, it doesn't fill me with confidence that I will find it there - but it's possible.
The GCD listing for Famous Funnies #214 notes two subsequent reprints of this image - one in Space Cowboy (3003), which is obviously not pertinent to our purposes - and another in The Rocket's Blast-Comicollector #110, cover-dated May 1974, which is much closer to the publication date of the Newton issue, but appears in itself to be an unlikely source for Newton.
A black and white version of Frazetta's illustration appears in a blog post concerning Frazetta's Famous funnies covers, but it does not reveal the source of the image.
For what it's worth, a parody appears on the cover of Normalman Funnies #8:
But that's it so far. As I say, I've been indexing the various Australian Unknown Worlds of Science Fiction issues, and would like to get some clarity on this before I blog the full details of those issues. Where else was this cover reprinted in the 1970's? My best guess is in an as yet unidentified Marvel magazine, but...
And my thanks to Mark Cannon and Mark Muller for helping out this afternoon - we had fun discovering what we know so far about this Newton poster!