There are ridges on coins to prevent counterfeiting
Have you ever considered why those coins are different sizes? Or what are they made of? You may have noticed that quarters and dimes have rough edges, while nickels and pennies do not. It is because coins used to be stamped with varied weights. It was first done to reflect the coin’s genuine value. But what about the ridges?
For as long as coins have been made from precious metal, coin clipping has been quite common. Therefore, for silver coins, reeded edges served a dual security purpose. First, they made the coins more difficult to counterfeit by adding an additional and complicated aspect to them. Second, they also helped to avoid fraud. A great way of keeping people honest.