Desert Wind Harley-Davidson custom made challenge coin. History of challenge coins - challenge coins surfaced during the World War I era. The practice of carrying a coin designed specifically for a unit was popular with the Army Special Forces. Carrying the coin at all times and presenting it when "challenged" to prove affiliation with that unit resulted in a number of consequences for those who could not produce a coin; the most popular required the coin less soldier to buy a round of drinks. That practice continues to be popular today.