Ever wonder why some coins have those little ridges along their sides? The answer goes back to 1792, when the Coinage Act established the U.S. Mint. That same act of legislation also specified that $10, $5 and $2.50 coins (known as eagles, half-eagles and quarter-eagles) were to be made of their face value in gold, while dollar, half-dollar, quarter-dollar, dime and half-dime coins were to be made of their value in silver. (Cent and half-cent coins were made of cheaper copper.) But a problem soon arose, after would-be criminals saw they could make a good profit by filing shavings from the sides of gold and silver coins and selling the precious metal. Before the 18th-century was out, the U.S. Mint began adding ridges to the coins’ edges, a process called “reeding,” in order to make it impossible to shave them down without the result being obvious. As a side benefit, the reeded edges also made coin design more intricate and counterfeiting more difficult.

The U.S. Mint stopped producing all gold coins during the Great Depression, thanks to an executive order from President Franklin D. Roosevelt, and a silver crisis in the 1960s led that metal to be gradually phased out as well. Today’s coins contain no precious metals—but you’ll still find those ridges, at least on half-dollars, quarters, dimes and some dollar coins. Aside from keeping up with tradition, the ridges also help make the coins distinguishable from each other by feel as well as appearance, enabling visually impaired people to tell the difference between similarly sized coins, like the dime and penny. So while coins made from precious metals may be history, it seems reeding is here to stay.