If you don't care for "buckle up, it's story time!", there's no need to read this fluff piece.

Coin ridges were invented to combat a sneaky little trick called coin clipping. This was basically the 17th-century version of skimming from the till: Clever criminals would shave small amounts of precious metal off the edges of coins, then spend the lighter coins at full value while melting down the trimmings to sell.