Officer clearly stated that it was a "Challenge Coin"
It's only a theory because that is what he clearly stated that it was when he gave it to POTUS.
I am not saying that it wasn't something other than a challenge coin…. hell, it could have been a thumb drive containing the entire Akashic Record for all I know, but the man said it was a coin, giving Presidents challenge coins is a thing, and also Occam's Razor.