When the money was invented by the Lydians it was a metal coin and even today we still use metal coins. Coins are usually forged out of a metal disk. The American dollar cent is forged out of a copper alloy. There are small details to fight counterfeits. A closer look on the penny reveals the small details that are not immediately visible to the naked eye. Millions of people who use pennies on a daily bases do not realize the embossed figures of Abraham Lincoln on the coin, which is only 100 micrometers across. Also under the microscope, it is possible to observe the discolorations of corrosion.