After looking at hundreds of comic book covers, it becomes quickly apparent that not every cover is 100% original. Whether done intentionally or even underhandedly, there's something about uncovering these "swipes" that adds a new element of fun to reading and collecting comics. Avengers #57 introduced the super-hero android, the Vision! Besides the main three Avengers (Cap, Iron Man, & Thor), he's probably served the most time on Avengers teams. His first appearance has been swiped a number of times since then, including Avengers West Coast vol. II #45, which featured a dramatic change in the character when his emotions were unwillingly removed.
Avengers #57 Avengers #57
October 1968
John Buscema
 Psychoblast #5 Psychoblast #5
March 1988
Robb Phipps
West Coast Avengers vol. II #45 West Coast Avengers vol. II #45
July 1989
John Byrne
 Cyberspace 3000 #6 Cyberspace 3000 #6
December 1993
 
Mighty Avengers #14 Mighty Avengers #14
July 2008
Marko Djurdjevic
On Ebay: Avengers | Vision On AtomicAvenue: Avengers