When I was in Korea in the early 70s, we were required to turn in our Greenbacks for military payment certificates (MPC). Looked very much like monopoly money. If you drew cash on payday, it was in MPC. Supposedly, one could not use MPC off post but it was commonly accepted. About every six months, they would call an alert and everyone would have to swap their MPC for new MPC. Usually only the color of the bills would change. Those that paid attention knew when the swap would happen because the Koreans would stop taking MPC a day or two before the swap. The day before you left Korea, you could turn your MPC in for Greenbacks. They stopped this in 1974 IIRC.
Thank you. That was the first and only post which actually addressed the topic. We could easily have the very same type of system in place.
Before that, there was the overprinted currency issued to Hawaii pre-WWII. That was in case the Japanese took them over, we could invalidate the currency. As a kid, I remember seeing a $10 bill like that and thought it was a commemorative and were doing it for each state.
But they kept their ration control plates through the end of the 80’s. I ended my military career with the Seoul Olympics ending and then I was returned home.