The Sotheby's auction house says the 1733 book sold for US$556,500 (S$809,300) on Tuesday to an anonymous bidder. The almanac's presale estimate was US$150,000.

The book was discovered recently at the local historical society in Berwick, Pennsylvania, north of Philadelphia.

Sotheby's written Americana expert Selby Kiffer says it's one of three known copies of the Franklin classic from 1733. He says he thought it was a facsimile until the binding proved to be original.

Sotheby's says it sold George Washington's copy of the Federalist Papers for US$1.4 million in 1990. -- AP