Organization
coin or medallion bearing an organization’s insignia or emblem
A challenge coin, also known as military coin, unit coin, memorial coin, or commander's coin, is a small coin or medallion, bearing an organization's insignia or emblem and carried by the organization's members. Traditionally, they might be used to prove membership to the issuing organization when asked or as a commemorative award. Historically, challenge coins have been presented by unit commanders in recognition of special achievement by a member of the unit, or the unit as a whole. They have also been exchanged in recognition of visits to an organization.