This is the cover to Newton Comics' The Avengers #3:
It has been slightly modified from the original which appeared on the cover of Marvel Comics' The Avengers #4:
The story contents are as follows:
Captain America Joins... The Avengers!, originally published in The Avengers #4, March 1964
Iron Man Faces The Crimson Dynamo!, originally published in Tales of Suspense #46, October 1963
I have compared both stories to reprints in Marvel Masterworks and Essentials editions and neither story appears to have been unduly modified.
The poster in this issue is a Jim Steranko double-page splash from Captain America #110:
This issue does not have a cover date but it appears it was published 9 August 1975. At this stage The Avengers was published every three weeks. The Avengers #2 was published three weeks earlier on 19 July 1975, and one of the in-house advertisements in this issue is for The Fantastic Four #3, which is advertised as On Sale Now and was published a week earlier on 2 August 1975. The expiry date for the contest in Fantastic Four #3 is 15 September 1975, and the expiry date for the contest in The Avengers #3 is a week later on 22 September 1975.
This issue also contains an in-house advertisement for Conan the Barbarian #1, which is advertised as On Sale 30 August 1975.
This issue was advertised as on Sale Now in The Incredible Hulk #4:
It is also worth noting that Newton skipped the reprinting of Marvel Comics' The Avengers #3. They would publish it shortly afterwards in The Avengers #6.