The pilot avoided German patrols by donning civilian attire, but all of his identification had been confiscated so he had no way to prove his identity. With great difficulty, he crept across no-man’s land and made contact with a French patrol that was on the lookout for German saboteurs dressed as civilians. The French mistook the American pilot for a German saboteur and prepared to execute him.
Desperate to prove his allegiance, the pilot pulled out the coin from his leather pouch and showed it to his French captors. One of the Frenchmen recognized the unit insignia on the coin and delayed the execution long enough to confirm the pilot's identity.
Once the pilot safely returned to his squadron, it became a tradition for all members to carry their coin at all times. To ensure compliance, the pilots would challenge each other to produce the coin. If the challenged pilot could not produce the coin, he was required to buy a drink of choice for the challenger; if the challenged could produce the coin, the challenger would purchase the drink.
During World War II, there was a story about an American soldier scheduled to rendezvous with Philippine guerrillas who carried a Philippine solid silver coin stamped with the unit insignia to verify to the guerrillas that he was their valid contact for a mission against the Japanese.