An auction gallery in Georgia is selling what?s believed to be one of the rarest coins ever made in the United States ? a $3 gold coin estimated to be worth up to $4 million.

The coin is believed to be a 1870-S $3 piece from the San Francisco Mint that was found embedded into a souvenir book in a bookstore in San Francisco, according to Steve White, owner of the Four Seasons Auction Gallery in Alpharetta, Ga.

?It?s one of two, maybe three, known to have ever been minted by the San Francisco Mint,? White told ?It?s almost folklore to have this kind of rare coin to be around.?

White said the only other 1870-S $3 gold coin known to exist was sold at auction in 1982 for $687,500. The coin will be auctioned on June 2 and White invited all potential buyers to bring an independent expert to authenticate the piece.

?It?s a big piece of American history,? he said. ?We expect the coin to bring in between $2 [million] and $4 million.?

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