After awhile, the tradition was lost to the Air Force for more than fifty years. Partially due to the high cost of coinage and the difficulty of creating special medallions. In the late seventies, a weapons systems operator who flew in fighter aircraft uncovered this story while doing a paper at Air Command and Staff College. Upon completing his studies, he brought the tradition back to his squadron. Modern technology enabled high quality casting of the squadron insignia at a reasonable cost. The practice spread rapidly, first to fighter squadrons throughout both active duty and reserve components, and then to other military units throughout the Air Force.
Nowadays, many groups within the military in general use challenge coins. One such group is my old navy rating, master-at-arms.
Some American Chung Do Kwan schools have picked up this tradition and award black belt coins to their black belts. Any martial art style or school may benefit from the use of black belt coins.