Those tiny grooves on the edge
Coin ridges were not invented for grip or decoration. They made it obvious when someone shaved precious metal off the edge of a coin.
Quick answer
Coin ridges were invented to fight a specific crime called coin clipping, shaving metal off the smooth edges of gold and silver coins to steal the metal. Once you added ridges, any shaved coin was instantly obvious. Isaac Newton pushed the design at the Royal Mint in the late 1600s. Today's coins aren't made of precious metal, so clipping isn't a risk, but ridges stuck around because they still deter counterfeiting, help vending machines tell coins apart, and let visually impaired people identify denominations by touch.
Technical name
Reeding or milled edge
Invented to stop
Coin clipping fraud
Smooth-edged coins
Pennies and nickels (US)
Still needed?
Yes, for different reasons
Those tiny grooves on the edge
From 1696 to 1727, Isaac Newton served as Warden then Master of the Royal Mint in England. He pushed hard for reeded edges as part of a major recoinage effort to clean up a currency crisis caused by, yes, widespread coin clipping. The same person who described gravity also helped design the edge of your spare change.
Myth vs Reality
They make coins harder to counterfeit, help vending machines verify denomination by texture, and let visually impaired people tell coins apart by touch. The original reason is gone, but the feature found new work.
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