Rare 1972 Penny Sells for $1.15M (PHOTO)

A penny dating back to 1792 has just sold for $1.15 million at an auction in Chicago. It is believed to be one of the oldest coins and is certainly one of the most rare.

The penny is made of copper surrounding a small bit of silver, which was added to make the coin heavier, Todd Imhof, executive vice president of Heritage Auctions told the Associated Press. Heritage Auctions was responsible for the sale of the coin.

What makes this coin so unique? One side features Lady Liberty surrounded by the phrase "Liberty Parent of Science & Industry," while the other side reads "United States of America - One Cent."

"Some 1792-dated cents have a silver plug as a proposed way to overcome a flaw in the Mint Act of 1972," Imhof told the AP. "That congressional law would have made pennies of the era too large and heavy for practical use, so the mint's chief coiner suggested making a smaller sized coin using a tiny silver plug with three-fourths of a cent worth of silver and a quarter-cent's worth copper surrounding it."

"After 200 years, we can only account for 14 of these," Imhof reported. He also stated that this particular penny was never in circulation, making it all the more rare. Congress decided to pull the silver plug from the coin, making it all copper, and those coins were not put in circulation until 1973.

The particular coin bought for $1.15 million had previously brought in $105,000 at an auction in 1974. Just last month a penny from 1973 brought in $1.38 million, which is "the most a United States copper coin has ever sold for at auction," the AP reported.

Both coins are known as "Chain Cent" by collectors, a reference to the linking rings around the coin.