I’m afraid to even ask what kind of useless, liberal BS symbolism a “Challenge Coin” is...
and is hardly a "Participation Trophy".
It's a bar game, that's taken seriously.
Among Warriors, you carry a challenge coin, which is a 1 3/4" dia. or so brass and enamel disc with a unit insignia on it. If a bunch are in a bar, and someone hauls out and slaps down his coin, everyone else has to show he's a member of the Frat, by meeting the Challenge to show his coin.
You don't have one, you buy the next round.
Even civilian contractors have challenge coins, with corporate logos on them. It's sort of an "I was There" symbol, when skin ink was against regulations. Faggot Lefties don't know...
I take it you've never been the military
You should do an internet search, first, prior to nibbling on your foot.