A recent Army article noted that the commander of forces in Afhganistan “coined” members of the US military for their exceptional performance:

Marine Gen. John R. Allen, commander of the International Security Assistance Force in Afghanistan…presented ISAF commander coins to six soldiers surrounded by their friends and fellow service members during a mid-day ceremony here.

After listing the accomplishments of the soldiers, the article included this summary of the tradition: 

The awarding of commander coins, also called challenge coins, dates back to the age when enlisted soldiers were not authorized the presentation of medals. Accordingly to legend, an officer would separate the ribbon from a medal, presenting the latter half to a soldier for a job well done. In modern times, coins denote membership to a specific unit and are often awarded to service members for special achievements.

That tradition is significantly different from that of the coins traditionally carried by fighter pilots, though the tradition of “coining” troops probably exists in all the services.  In any case, getting “coined” by a four-star general is a significant event.