Jack Kirby's original artwork for a 1968 edition of comic book The Mighty Thor has soared past its estimate at Charterhouse Auctioneers in the UK.
The lot was expected to make up to £8,000 ($10,552), but realised £36,000 ($47,486) instead on June 24 - an increase of 350%.
Thor is one of Marvel's most popular comic book heroes.
He first appeared in the Journey into Mystery series during the 1960s and rapidly became its standout character.
The comic book was later renamed after him.
Meanwhile, Jack Kirby is one of the most acclaimed artists of the silver age of comic books and his work regularly pulls in hundreds of thousands of dollars in the US.
The consignor received the piece as a gift from her father in the 1970s and was entirely unaware of its value until recently.
A spokesperson from Charterhouse Auctioneers told the Guardian: "Sometimes when you own a piece of art and hang it in your house, no matter how much it is worth, you don't automatically put a value on it.
"You get used to it being a piece of art in your house. Marvel has grown increasingly popular in recent years.
"Out of curiosity, the owner got in touch… and we were able to assess the art and make the owner aware of the value."
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