Hello everyone, Two items from my collection.. A rim burr on a coin is a genuine mint error that happens when excess metal, jagged tabs, or debris from manufacturing equipment get caught and struck into the coin's outer rim. What Causes a Rim Burr Cutting and Shaping: They form when moving parts—such as the upsetting mill, feeder fingers, or a chipped cutting/blanking tool—leave behind a small metal projection or roughness before the coin is struck. The Struck-In Process: loose metal fragments or folded pieces get trapped against the planchet and flattened directly into the rim or edge junction under massive striking pressure.