I would like to start off by saying this is an awesome site. There are many great items on here that can not be found on other sites with military memorabilia.
10th Special Forces Group Challenge Coin Silver
What is a challenge coin?
Challenge coins were originally used by Special Forces to recognize soldiers for outstanding acts, team training, unit identification, to boost esprit de corps, and to build camaraderie. Today, all military and many law enforcement units have challenge coins. Traditionally, "coining" was executed to see if fellow soldiers were carrying their unit's coin. In the Viet Nam era this tradition was modified slightly so that the loser of the challenge (Not carrying a coin) was obligated to buy a round of drinks. Today Challenge Coins are handsomely presented in display cases for everyone’s enjoyment. Many people trade these coins at training and collect other department/unit coins.