Coin edges may be plain (smooth) or patterned, or a combination of both. They can also include lettering.
Reeded edges are often referred to as "ridged" or "grooved" (US usage), or "milled" (UK usage).[1] Some coins, such as United States quarters and dimes, have reeded edges. Reeding of edges was introduced to prevent coin clipping and counterfeiting.[2] [3]
The main techniques of coin edging are edge mills of various types, which put a pattern on a smooth edge, after a coin and coin mills with edge rings, which pattern the edge at the time when the coin is being milled.
Examples of patterns used on coin edges include: