A rare leather-bound book that played an influential role in America's early history could bring a windfall for a soldier training for his second tour in Iraq.

Indiana National Guard Capt. Nathan Harlan was a high school junior when he paid $7 for a 1788 first edition of volume one of The Federalist — a two-volume book of essays calling for the ratification of the U.S. Constitution.

Harlan, a 35-year-old from Granger, Ind., said he always thought his find might be worth about $500, not the thousands it could fetch when it's sold online Tuesday by Heritage Auction Galleries of Dallas.

"I'm really hoping it goes for $100,000, but I'm not holding my breath," he told The Associated Press.

The divorced father of three was 16 when he bought the 227-page book in 1990 after his mother spotted it among book stacks as they browsed at a South Bend, Ind., flea market.

Harlan's high school history class happened to be discussing The Federalist — also known as The Federalist Papers — that same week, so he knew the book was special.

The two-volume set was published months after the Constitution was drafted in September 1787 in Philadelphia. Its collected essays helped rally support for ratifying the document that provided the federal government's framework, said Mark Dimunation, chief of the rare book and special collections division at The Library of Congress.

The essays were penned by James Madison, Alexander Hamilton and John Jay, all of whom used the same pseudonym to focus attention on their pro-ratification arguments.

"It's one of the great political documents to come out of America," Dimunation said. "And the favorite parlor game of the late 18th century was who wrote which essay."