(AP) †When is a penny worth $1.15 million? When it is a rare experimental penny minted in 1792.

The unusual coin was auctioned off April 19 at the Renaissance Schaumburg Convention Center in suburban Chicago.

Officials with Heritage Auctions say Kevin Lipton of Beverly Hills, Calif., bought the penny on behalf of a group of unnamed investors. The winning bid was $1 million, but the investors also must pay the auction house’s 15 percent commission.

The coin is made from copper and encases a small plug of silver.

The silver was added to make the penny heavier, said Todd Imhof, executive vice president of Heritage Auctions. On one side of the coin, a depiction of Miss Liberty is ringed by the phrase “Liberty Parent of Science & Industry.” The back of the coin reads “United States of America One Cent.”

“After 200 years, we can only account for 14 of these,” said Imhof, who added that the penny was never actually put into circulation.

The same coin was last sold at a public auction in 1974, when it went for $105,000.

“It’s a real classic, one that’s rarely seen in such good condition,” Imhof said.