These are known as challenge coins. They're pretty interesting and I have a large selection from my own career.
Here's a thread on leper coins: https://www.cointalk.com/threads/leprosy-colony-coins-data-previous-thread-links.203823/
Another Daniel Dupuis medal. Late 1800 Military Preparation prize offered by the Minister of War. Award for achievement during Military Training.
They're some nice "coffee can" pieces, SchwaVB57. I especially like the hobo nickel. Is there any engraving on the reverse? Bruce
It's just what they're called. There are all kinds of stories about them but if you're interested I can link an article where a serious numismatist discussed their origin. Essentially they're used as a way of acknowledging outstanding performance or as a token of membership in a into, project, etc. Let me know if you want to read it and I'll post the link.
http://www.coinbooks.org/club_nbs_esylum_v14n18.html#article4 Check it out! Here's an early example of a challenge coin I purchased:
@Jwt708 - Thank you very much. I just printed it out(my eyes/bi-focals give up at times) and can't wait to read it.
The article by Ray Bows is the one to read, he is a very knowledgeable numismatist who specializes in military monies.