Earlier quoted context omitted.
If you are in the military, you can use challenge coins to get yourself free drinks. The idea is that when everyone is at a bar, the guy or gal with the challenge coin from the highest ranking officer never has to pay for rounds of drinks. I've never seen a civilian use one. We don't spend much time in bars, and the feeling I get is that if I did try to whip one out in the presence of uniformed personnel -- a challen…
How long are challenge coins "valid"? If someone had a challenge coin from Eisenhower (not sure those exist, let's pretend they do) would that person essentially always win, forever?
Which "axes" are in play, and who "wins" (or ties, a lot of the rule variations I've heard are set up to optimize towards ties; the most common challenge is just whether or not the other person has a challenge coin of any sort, not necessarily trying to figure out which wins if both people have coins on them) varies a lot between groups.
Also, challenge coins have seeped into some parts of lay culture, especially bar culture (given that alcohol has always been the big bet, it shouldn't be a surprise). For instance, the liqueur Fernet has its own challenge coins that bartenders tend to challenge each other for free shots of Fernet. (Bars try to keep one in reach of the bar at all times in case the bar is challenged, and the number of people that have them that have them that aren't themselves bartenders is supposedly kept quite rare.) https://talesofthecocktail.com/history/part-family-behind-sc...