An extremely rare $1,000 bill described as the “Holy Grail of paper money” has been sold at auction for just over $2 million.

Auction house Stack’s Bowers Galleries sold the unusual bill for $2.04 million on Thursday evening at the 2018 Winter Whitman Expo in Baltimore.

The 1890 Treasury Note is dubbed the “Grand Watermelon” on account of the large green zeros on the back of the bill. Major General George Meade, the commander of Union forces at the Battle of Gettysburg, is shown on the bill’s face.

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Only seven “Grand Watermelon” notes are known to exist. “The Grand Watermelon note is one of the rarest and most sought-after pieces of American paper currency,” said Stack’s Bowers President Brian Kendrella, in a statement. “This is one of only three known to exist in private collections and the finest example of its kind.”

When it was last sold, in 2005, the note became the first ever paper bill to break the $1 million mark.

One of the very first pennies produced in the U.S., a 1792 Birch Cent, will be auctioned at the Whitman Expo on Friday. The coin is estimated to be worth $1 million.

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Commissioned by Thomas Jefferson, only a handful of Birch Cents were minted as an example of what the newly-formed U.S. government was considering producing. The coins were seen firsthand by Jefferson and George Washington, according to Stack’s Bowers.

Rare coins are big business. In 2015, another Birch cent sold for almost $1.2 million at auction, the Guardian reports.

A 1913 Liberty Head nickel was recently auctioned by Stack’s Bowers Galleries for $4.56 million. The Liberty Head nickel is one of only five in existence.

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Earlier this year, a small $5 gold coin produced by the San Francisco Mint during the height of the California Gold Rush was estimated to be worth “millions of dollars.” The coin’s owner had initially thought that the money was fake.

Fox News’ Frank Miles and Chris Ciaccia contributed to this article. Follow James Rogers on Twitter @jamesjrogers