I've been in bars before when someone whips out a challenge coin, but since I'm not in the military I don't really understand this custom. What's the proper protocol for challenging someone in the military with a one of these coins?
There is a long standing tradition of challenging fellow military personnel with your challenge coin. This is how you do it. First, it is best if you do challenges with your coin in a military bar, or in a bar with only mostly military personnel present (for ethical and etiquette reasons). Challenging someone, you whip out your coin and slap it down on the bar. You can issue general challenges (to everyone at the bar) or to a specific person. If the person you're challenging has their military coin with them (typically carried in the pocket), then they pull it out and slap it down. Everyone you are challenging either has to show their coin or risk paying the penalty. If someone does not have their coin with them, then they are required to buy a round of drinks for everyone who does have their coin. If you are issuing the challenges, and everyone you are challenging has their coin and can show it, then you are required to buy a round of drinks for everyone. It is a tradition that is intended to build camaraderie and friendship within various units and ranks of the military, and shouldn't be used to get a new recruit to buy you drinks.
Do you have to be in a bar to issue a challenge check?
No. Technically, you can be anywhere. It is most common in military bars, but you can issue a challenge check anywhere. If you don't have your coin with you, you may have your coin confiscated by the issuing agency. Coin checks are often a sort of initiation for new members of the military.
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