Many people say pennies are not worth saving. After all, a penny is only worth a cent. But one unusual penny turned out to be worth a lot more when a coin collector paid $1.7 million for it earlier this month. The coin is one of a kind. It is the only penny that the Denver mint  made out of copper, instead of steel, in 1943. Because it is unique, it is also very valuable. No penny has ever sold for so much money. The Changing Penny The Lincoln penny first appeared in 1909. For 34 years, the one-cent coin was made out of copper. Then, in 1943, the penny changed. World War II was going on, and copper was needed for equipment. So for one year, pennies were made out of steel instead. At least most of them were. Only a few coins were made out of unused copper. There are three main mints, or places where coins are made, in the United States. Of the known copper pennies from 1943, twelve were made in the Philadephia mint, and five were made in the San Francisco mint. Only one was made in the Denver mint. Nobody knows for sure why a copper penny was made at the Denver mint in 1943, coin dealers Andy Skrabalak toldTime for Kids. "There is a rumor that a mint employee made the coin in the middle of the night." A Special Set The coin collector who bought the $1.7 million penny wants to remain unknown. But the reason for the trade is known. He already had two copper pennies from 1943 - one from the San Francisco mint and one from the Philadephia mint. To complete the set, he needed the Denver penny. The three coins will go on display at a coin exhibition in Tampa, Florida. The collector who sold the penny is also keeping his name a secret. It took four years to convince him to give up the rare coin. Now that he has finally donating all of the money to charity. What can we learn about the collector who sold the penny?
He already had two copper pennies from 1943. He wanted to complete the set of copper pennies. He didn't want to sell his penny in the beginning. He was a well-known coin dealer in Tampa, Horida.