@Markus1959 is right. I wouldn't pay much over 10 since they were likely passed out to returning service members.
Right - they are called "CHALLENGE COINS" - my son-in-law has quite a few from the Marine Corps. And that is pronounced "core" not "corps" like our fabulous Pres said!! (Not a political statement - just factual!! )
See this thread I started almost 3 years ago: https://www.cointalk.com/threads/challenge-coins.218228/ Here's my gallery of challenge coins: https://www.cointalk.com/media/albums/challenge-coins.122/ I'm a big fan of challenge coins. The below link is to a review from Ray Bows and he discusses challenge coins a bit. Worth a read. http://www.coinbooks.org/club_nbs_esylum_v14n18.html#article4
Anyone can buy "challenge coins" - it takes a special person to actually earn and be proud of them!!!
I agree. Mine were both bought and earned - I'm active duty Air Force, about to hit my 12 year mark The ones earned are much more special than the ones bought but they do tell a nice story of my career so far. In the Air Force squadrons usually make coins and sell them to raise funds for things like Christmas parties. Designs usually change with each new commander.