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© Bloomberg via Getty ImagesThe United States Mint in Philadelphia, Pennsylvania

A former federal cop assigned to the U.S. Mint in Philadelphia admitted stealing $2.4 million in "error" coins.

William Gray, 64, of North Wildwood, N.J., admitted in federal court that he took the $1 presidential coins, all missing edge lettering, and sold them to a California coin dealer. Gray pleaded guilty to theft of government property and income tax evasion, said U.S. Attorney Paul Fishman.

Gray had worked at the U.S. Mint since 1996. He said he took the coins knowing they would be considered more valuable to collectors because they were considered "mint errors." He mailed them from New Jersey.

He was freed on $50,000 bail and will be sentenced on Dec. 20.