The challenge coin (or RMO - for "Round Metal Object") is one of the more obscure traditions in the military. A challenge coin can be as small as an American nickel or as large as a casino chip; silver or golden in color, or painted brightly; milled or smooth. Across all versions of the myth, several facts remain the same:

  • You always carry your coin--a soldier's day to day manifest will almost always include a military ID, cash, and an RMO.
  • Your challenge coin will usually have your unit's crest on one side, and can be laced with pictorial in-jokes like some service academy class rings are; the challenge coin is also called the "unit coin" or "unit RMO" for this reason.
  • When challenged to produce your coin, the penalty for failure is the purchase of alcoholic beverages for all involved in the challenge.
  • If all challenged successfully produce their RMO, the challenger gracefully takes the penalty on him- or herself.

The rules of engagement vary as widely as the stories about where the coins come from. In some circles, simply saying the word "coin" is a challenge. In others, one must specifically and formally state the challenge: "Sergeant, produce your coin or buy a round of drinks." "Lieutenant, here is my coin; where is the round of drinks?" Some prefer unspoken challenges, where the loud clink of a coin on the bar is the signal to produce. In some versions, handing one's coin over is considered a forfeit, where it may be considered common courtesy elsewhere. The bottom line about the rules: find out what rules your unit (and more importantly, your colonel) plays by as soon as possible after acquiring your coin.

But where do you get one? Well, that's another confused story. Some enlisted associations will sell RMOs to raise funds for unit activities. Some units sell them in their gift shop. Occasionally, a unit will have several types of coins in circulation at the same time: a cheap, publicly available coin, purchased for $5.00 at the gift shop, and the more ornate "Commander's Coin" or "Chief's Coin", given by the commander or chief of a unit for a job well done. These are usually the normal unit coin painted with enamel paints. I was personally passed a coin in a handshake by a colonel who felt my briefing had contributed to his unit's mission; I didn't realize the coin was being passed, and missed my chance to have a colonel's coin. Generals will give out their RMO on a whim while taking a tour of another unit--sometimes you just need to ask, sometimes it's passed in a handshake, and other times you'll find it on your desk in an envelope the day after the General comes by. In this manner, the challenge coin is positive reinforcement: everyone in a small unit will know who has the Colonel's, Chief's, and General's coins, and they're usually the role models.

As for the origins, well, nobody makes up bullshit like the military, and due to some creative license by unit historians throughout the past, the true origins are probably beyond recovery. I present, in historical order, some of the more prevalent stories about why we carry RMOs (followed by footnotes explaining why I feel the story is dubious at best):

  • During World War I, American volunteers filled the newly formed flying squadrons. In one squadron, a wealthy lieutenant1 ordered medallions struck in solid bronze carrying the squadron emblem for every member of his squadron. He himself carried his medallion in a small leather sack about his neck. After he was shot down, taken POW, and escaped, he had only the leather sack to identify himself to the French as friend or foe--he produced his coin, and was rewarded with their hospitality (instead of a certain death), as well as a bottle of the local vintage when he recovered and was sent home.
  • In World War I, aviators often carried a handgun into their only-mostly-reliable biplanes and triplanes, so that if they crashed, they could defend themselves against a small team of potential captors. Often, these flyers and their crewmen each had a bullet especially engraved or marked with the unit insignia or abbreviation. They carried these bullets as a good luck charm, which inevitably found itself as a conversation piece in the English pubs that pilots frequented during and after WWI. The habit of showing off one's bullet evolved into slamming the bullet down on the bar, primer end down2, in a challenge to a fellow squadron-mate to see who had to buy the next round. Commanders knew the futility of trying to do away with one of the flyers' favorite off-duty pastimes, so instead they brought the campaign coin into being. The "unit coin" became a new institution.
  • The coin as a unit symbol can be traced to the guerilla force under General Blackburn, who fought against the Japanese occupation of the Philippines during World War II. This combined force of American, Filipino, British, Australian and other allied nations engaged in classic guerilla tactics -- striking hard and disappearing into the jungle before the conventional Japanese forces could react. In order to make contact between guerilla bands who had never met each other, they adopted the expedient method of filing a one-peso silver coin clean on the back and stamping their unit emblem into the metal.3 Upon meeting, the leaders would reach into their pockets, and bring out a handful of change. Among the change would be their unit RMO, thus serving as a secure and discrete method of identification.
  • In Vietnam, men who had seen combat joined "Bullet Clubs": informal groups of friends who would challenge each other to produce a bullet to prove that they had seen combat. The logic was that any man who had seen combat with the Viet Cong would always carry a bullet to deny the enemy personal capture. At some point, things got out of hand4, and men began bringing in larger and larger rounds: .50 caliber machine gun rounds, aircraft tracers, and 20-, 40-, and 105-mm artillery shells. Clearly, these were not personalized Coup de Grace munitions but rather manifestations of perceived individual prowess in combat, or perhaps on R & R. At the height of the Bullet Club's heyday, it was not an uncommon sight to see strewn across a barroom table a very respectable representation of the full range of bullets, rockets, cannon and artillery shells used in Southeast Asia. As in the above bullet story, good sense--probably in the form of a worried bartender or colonel--stepped in and replaced the bullets with unit coins.

As you can imagine, there are countless other versions these out there, as well: take your pick. My color commentary on the possible validity of these is below, but don't take my word for it. If you find yourself in the bar with one or more military members, ask about their RMO--you may just get a drink out of it.

I'm indebted to several public affairs employees: soldiers, sailors, marines, and airmen--who have tried to hunt down the origins of the RMO and posted their authoritative stories on the web, some on official government webpages. None cite sources more than 10 years old, so my paraphrasing is probably more paraphrasing of their paraphrasing.
1 - Ha! Everyone knows there's no such thing as a "wealthy lieutenant." Sounds hokey and contrived, anyway.
2 - Evolved? Slamming live ammo on a table sounds like evolution in action to me.
3 - This one sounds plausible, except: what did a lightly armed, fast-moving guerilla force stamp their coins with, a field expedient mint?
4 - I can see this one being true, if only because "things got out of hand" describes most of the Vietnam War.