The edges of a quarter might feel pretty groovy, but all of those ridges were once a serious weapon in the war on crime. When the United States first began minting its own coins, they were made using silver: a dollar coin contained a dollar’s worth of silver, etc. This makes a lot of sense, but it gave rise to a kind of criminal called a “coin clipper.” These thieves would shave off small amounts of the silver to keep for themselves, and then spend the coins as if they were worth their full value. The solution to this was those little grooves—called “reeded” edges—which made it immediately obvious when someone tried filing them down. These days, the metal in our coins has very little intrinsic value, yet the ridges remains as a tactile way of distinguishing between denominations.