There are coins issued by the military, by schools, by interest groups, by organizations, and by hobbyists that fall into the category of challenge coins, pogs, and geocaching coins.
Some schools issue them and have students challenge each other, some colleges and sports leagues issue them for their teams, some organization issue them for motivating members, some issue them for badges (Boy Scouts), some for game challenges (Pogs), and others are for tracking like geocaching.
A challenge coin is a small coin or medallion (usually military), bearing an organization's insignia or emblem and carried by the organization's members. Traditionally, they are given to prove membership when challenged and to enhance moralte. In addition, they are also collected by service members, and are used by higher-ranks to recognize team-building actions of lower ranks. They can be given out for good grades, good attendance, winning games, and more at schools. They can come in many different shapes and sizes.
POGS originally were a game created by a school teacher in Hawaii using milk bottle caps in the game played by students. The cardboard was weak after playing, and today POGS are no longer made of cardboard. The Army and Air Force Exchange Service (AAFES), the U.S. military’s merchandise supplier, began supplying troops with POGS in 2001 for use as army currency, aiming to cut down the weight of shipping heavy nickles and dimes overseas. With the official name “POG gift certificates,” AAFES POGS maintained the name and size of the schoolyard game with a simpler design. The army POGS were released in 5, 10, and 25 cent denominations and are still used to this day to buy items from AAFES stores around the world. Hollywood got on board and issued game POGS with images like Power Rangers, and next came POG Slammers. The most popular POGs today are Marvel Comic ones.
A Geocoin is a special coin created by individuals or groups of geocachers as a kind of signature item or calling card. Like Travel Bug® Trackables, each Geocoin is assigned a unique tracking ID which allows them to travel from geocache to geocache or to be passed amongst friends, picking up stories along the way. Geocoding and Geocaching has taken off worldwide. Check out these websites: