The original versions of Alex Ross' cover paintings for Superman: Peace on Earth and Batman: War on Crime are up for auction.

The works are available as part of Heritage Auctions' Sept. 8-12 Comics and Comic Art Signature Auction. Both gouache paintings were crafted on Bristol board and measure 13 inches x 17.5 inches. The Superman: Peace on Earth painting is expected to sell for more than $21,000, while internet bids for the Batman: War on Crime art are currently at $13,500.

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Superman Peace on Earth Heritage Auctions artwork
Batman War on Crime Heritage Auctions artwork

"These two covers are incredible as a pair -- incredible images of two of the most iconic superheroes of all time, rendered impeccably in Ross's trademark style and both coming from what most collectors consider his most desirable period," Heritage Auctions Vice President Todd Hignite said. "Iconic is a term likely overused in our field, but these originals absolutely qualify."

Superman: Peace on Earth and Batman: War on Crime were both published in 1999 as a duo of prestige-format collaborations between Paul Dini and Ross. The former saw the Man of Steel working to inspire the people of Earth during the Christmas season, while the latter featured Batman rebuilding a neighborhood of Gotham City and confronting a young man who also saw his parents die.

Both books won a flurry of awards, with War on Crime receiving both a Harvey and an Eisner in 2000. The books were the precursor to four other Dini and Ross works, including Shazam: Power of Hope and Wonder Woman: Spirit of Truth, which were later categorized as The World's Greatest Super-Heroes series.

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Source: Heritage Auctions