The copy of Tales of Suspense #39 has fetched a record sum from an auction at ComicLink.
The comic is graded 9.6 on the Certified Guarantee Company (CGC) scale, reports ComicBook.com.
There have only been three copies of the issue graded as highly since the founding of CGC and none higher. A 9.4 copy - the next highest-graded - was sold by ComicLink in January for $145,000 (£89,000).
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If the pending sale goes through, Tales of Suspense #39 will become one of the ten most valuable comic issues and the second most valuable Silver Age comic after Spider-Man's debut in Amazing Fantasy #15.
Iron Man was created in collaboration by Stan Lee, Jack Kirby, Larry Lieber and Don Heck.
Iron Man is currently being portrayed by Robert Downey Jr in Avengers, the actor's third outing as Tony Stark.