Coins have ridged edges for a clear reason
We all adore money, yet we never stop to consider why it seems the way it does. It pays for everything, so why don’t you just shut up and use it?
You might want to go back to the 16th century if you’ve ever wondered why coins have stiff edges. People would clip little bits of valuable metal from coins to sell at the time while passing on damaged coins for full value. To counteract this, a procedure known as reeding was developed, which entails carving a number of grooves on the edges of coins so that you can tell if they’ve been tampered with. Reeding has been practiced for centuries.