After 80 hours of volunteering you can earn a challenge coin.
During WWI, a squadron Lieutenant ordered medallions struck in solid bronze carrying the squadron emblem for every member of his squadron. Many of the pilots carried their medallions in small leather sacks tied around their necks.
One of the pilots after acquiring his medallion was shot down behind enemy lines. The pilot was then captured by the Germans. During the days of transport to a prisoner of war camp all of the pilot's personal identification was removed by the Germans except for the small leather pouch hung around the pilot's neck that contained his squadron medallion. In the process of the transport the pilot was taken through a French town near the front. While passing through the French town, it was bombarded by an allied attack, during this attack the pilot escaped and managed to evade German patrols by dressing in civilian clothing.
Eventually the pilot stumbled into a French resistance outpost. Unfortunately the French resistance had been plagued by saboteurs who sometime masqueraded as civilians. Not recognizing the young American's accent the French thought him to be a saboteur and intended to execute him. Just prior to being executed the pilot remembered his leather pouch containing his squadron medallion and displayed it to his would be executioners. One of the pilot's captors recognized the squadron insignia on the medallion and delayed the execution long enough to confirm the pilot's identity. Instead of shooting him they gave him a bottle of wine and returned him to U.S. Forces. (Hence the coin check and buying drinks)
Once back at his squadron, it became tradition to ensure all squadron members carried their coins at all times. This was accomplished through coin checks. (See Coin Checks)
As time went on Special Forces, elite military units and tactical teams have a long history of carrying a challenge coin to identify past and present members. These coins are also minted to help solidify important team concepts that are necessary for successful coordinated team missions. The concepts that are helped solidified by challenge coins are team cultures, loyalty, boosting of morale and building of camaraderie.