The cover image first appeared on the cover of Marvel's Conan the Barbarian #20:
Newton Triple Action #1 is cover-dated August 1976, but it was likely published 31 July 1976.
The story contents are as follows:
The Bitter Taste of Defeat!, originally published in The Avengers #21, October 1965
Among Us Stalk…The Sentinels!, originally published in The X-Men #14, November 1965
The Black Hound of Vengeance!, originally published in Conan the Barbarian #20, November 1972
Blood Purge!, originally published in Savage Tales #10, May 1975
[One Knight's Stand], previously unpublished
Just as Newton Four-In-One #1 mopped up unpublished stories queued from cancelled series such as The Incredible Hulk, The Mighty Thor, The Invincible Iron Man and The Amazing Spider-Man, Newton Triple Action performs a similar function for the cover features The Avengers, The X-Men and Conan the Barbarian.
The final story is Jan Scherpenhuizen's [One Knight's Stand] which I've detailed previously.
This issue was advertised in other August 1976 cover-dated Newton issues:
My copy of this issue does not contain the free King Size Super-Hero Poster but it was likely either The Sub-Mariner and The Human Torch, The Amazing Spider-Man and Friends, or Thor.
This issue includes in-house advertisements for Newton Four-In-One, Planet of the Apes #17 and Dracula.
The indicia refers to this issue by the title Newton Triple Action, and as Vol. 1 No. 11. It is also copyrighted 1975 by Newton Comics Pty. Ltd. I've said this before but from this point on the Newton Comics indicia would often not only be inaccurate but rather bewildering.