from web site
History of the challenge coin runs along with the military tradition. Still, it’s the same in military departments but as the time has passed, these coins have become the trend and gained outstanding popularity in the civilian world. Hence the use of Custom Coins became the ultimate and rolled out its boundary to the following extent.
http://webonlinestudio.com/blog/4-ultimate-uses-of-custom-coins-to-make-a-divergent-look/