Not by me or anyone I served with, maybe it is a term that has been adopted. They are unit coins or service coins. They commemorate a unit, event, military service heroic act or some other solemn event.
Challenge coins is a bar game. Never played it myself. A company that makes some of these type coins is called "Challenge Coins". Every company needs a gimic.
It would be an awful thing for someone to use those coins that were placed on the memorial today to win a beer. Wouldn't it?
I heard it first used by Shep on Fox News.