The challenge coin is a worldwide, long-established tradition in the finest military and professional organizations. It symbolizes not only your membership in a professional organization, but your brotherhood with your fellow members -- in some combat units, the unit challenge coin is believed to bring the holder good luck and mission success. Thus, the RPA Challenge Coin is no cheap trinket. It's a symbol of your membership in one of the finest warbird organizations in the country. And with that membership, the holder of the Challenge Coin must at all times uphold the rules governing this historical tradition. Although you may personalize your coin by etching your call sign or tail number (a raised space is provided), you should not otherwise disfigure your coin with such things as holes drilled to attach strings or necklaces. You must always carry the unit Challenge Coin when in the presence of other members, as it represents your membership in, and commitment to, the brotherhood that binds this organization. At any time, but generally at the hotel pub after a long day of flying our warbirds, any member may "challenge" all RPA members present, usually by tapping the coin on the bar. Whereupon, you must promptly produce your unit coin and join in the chorus of coins, or "buy the round" for being among your unit without your trusted coin. Never drop your coin accidentally, for if this is done in earshot of your fellow members, it will be received as a challenge, and coins will be produced; if all present have a coin on hand, a future round will be on you. Such coins have been produced for most military units, including the Thunderbirds and almost all Army, Air Office and Navy combat units. The RPA Challenge Coin - a symbol of our membership, our esprit de corps and our organizational success. All coins are numbered and of top quality and shows the RPA logo "Winged Star" with a formation of our most plentiful warbirds on the back, the CJ-6, Yak 52 and Yak 50.