DALLAS, TX.- A previously unknown 1854-S Liberty Head Half Eagle — considered among the rarest of all U.S. coins — will be offered by Heritage Auctions after the firm was selected to bring the specimen to auction. Initially believed to be counterfeit, the gold coin is just the fourth specimen known to exist and will be the first to appear at auction since the 1982 sale of the Louis Eliasberg Collection.

"This discovery rewrites numismatic history," said Jim Halperin, Co-Founder of Heritage Auctions. "We are delighted to have been selected to auction this major find."

A New England man discovered the coin and sought the opinion of collectors and dealers who claimed it must assuredly be fake because of the coin's legendary rarity. Records indicate the San Francisco Mint struck just 268 Half Eagles in 1854, an extraordinarily low mintage for a U.S. gold coin produced during the California Gold Rush.

Of the three other known surviving examples, one is in the National Numismatic Collection at the Smithsonian Institution in Washington, D.C., and another remains in a private Texas collection. No one has seen the third coin since armed robbers stole it from the wealthy duPont family in 1967.

Seeking a final answer, the discoverer submitted his coin to the Numismatic Guaranty Corporation for authentication. After verifying the coin was not the stolen duPont specimen, NGC enlisted the help of the Smithsonian Institution, which provided photographs of its coin. The firm determined coin was authentic and graded the discovery as NGC XF 45, adding the phrase "Discovery of a Lifetime" to the coin's certification label.

"It's like finding an original Picasso at a garage sale," NGC Chairman Mark Salzberg said in a statement. "It's the discovery of a lifetime."

Heritage Auctions will present the previously unknown 1854-S Liberty Head Half Eagle in its Aug. 16 Platinum Night Auction during the American Numismatic Association's World's Fair of Money in Philadelphia.