police stone giant Challenge Coin
There is another story about an American soldier scheduled to rendezvous with Philippine guerrillas during WWII. As the story goes, he carried a Philippine solid silver coin that was stamped on one side with the unit insignia. The coin was used to verify, to the guerrillas, that the soldier was their valid contact for the mission against the Japanese.
The challenge coin tradition has spread to other military units, in all branches of service, and even to non-military organizations as well as the United States Congress, which produces challenge coins for members of Congress to give to constituents. Today, challenge coins are given to members upon joining an organization, as an award to improve morale, and sold to commemorate special occasions or as fundraisers. In the Air Force, military training instructors award an airman's coin to new enlisted personnel upon completion of their United States Air Force Basic Military Training and to new officers upon completion of the Air Force Officer Training School
