Where do the bills come from and how is the supply controlled? US currency of the generation pictured isn't child's play to counterfeit, so it has to be the government or some sophisticated entity doing it, and what are they getting in exchange?
If it's the government doing it, then how is this not just official NK currency that just happens to look like US (except for the opportunity to take it outside NK and use it as US)?
DPRK is notorious for producing bulk quantities of very high-quality counterfeits. it is a big export for them.