Newton Comics' The Avengers #1 was published 28 June 1975:
The cover image originally appeared on The Avengers #1. There is some recolouring evident, and possibly some minor linework extension along the borders.
The story contents are as follows:
The Coming of The Avengers!, originally published in The Avengers #1, September 1963
The Origin of Dr. Strange, originally published in Strange Tales #115, December 1963
Dr. Strange Master of Black Magic!, originally published in Strange Tales #110, July 1963
Comparing the reprints in this issue to the original stories (as they appear in my Marvel Masterworks volumes) this edition does not suffer excessively from Newton's predisposition towards culling and reformatting pages. The most notable editing occurs on the splash page to The Origin of Dr. Strange:
This is the same page in Marvel Masterworks Vol. 23:
The text box in the original issue refers to the origin story being told after a few Dr Strange stories had already been published. This is redundant in the Newton edition as this is the first Dr. Strange story they published in their new comic books (the character previously appeared in the Sunday Observer comics supplement) - so Newton filled the text box with a redundant sub title.
There is also some partial cropping at the bottom of the splash page to The Coming of The Avengers! splash page in order to print the indicia:
This page is reprinted in full in Newton's Origins of Great Marvel Comic Heroes:
Apart from this there are minor slippages in which the original page numbers escape erasure.
The poster in this issue is The Thing:
This issue was advertised in-house:
This advertisement is scanned from The Incredible Hulk #2.
On 29 June 1975 a full page advertisement for the issue appeared in the Sunday Observer:
As per the advertisement for The Incredible Hulk #1 a week earlier, the cover to the first issue appears beneath a larger image referencing the modern incarnation of the team. This is a composite image which originally appeared in a Marvel calendar for April 1975:
Forensically, The Vision is from the cover of The Avengers #57; Iron Man is from the cover of The Avengers #58; and Captain America is from the cover of Captain America #154.
The Scarlet Witch is image is an interesting case. I haven't identified this image in a comic book, but the image was used on a card in a board game in 1978:
The same set of cards employed the image of The Vision as per the calendar:
The Scarlet Witch appears to be a stock promotional image for merchandising purposes so it likely appeared on a number of products, but was certainly in circulation from as early as 1975.
The Thor source eludes me for the moment. The consensus amongst my operatives is that it is a John Buscema illustration. TBC.
Kudos to Neil Hansen for providing a scan of the calendar and identifying it as the source for the advertisement. Special mention to Mark Muller for identifying the Scarlet Witch image and providing scans. Mark's sleepless night scratching that itch until it bled was all for a worthy cause. And thanks to Mark Cannon for pitching in on our collective enterprise to identify the components of the composite, which engaged us for much of the day yesterday and was loads of fun.