According to recent reports from North Korea these "donpyo" or "tonypo" vouchers are being issued because the Central Bank lacks security paper and ink to print currency as a consequence of current sanctionns.

These are being used in payment by State enterprises and are used in commerce, not only by the "hard currency" stores, but there are problems because some merchants are refusing or discounting them because they are not sure the Central Bank will accept them. In practive they are being traded at a discount.

In November the Government started sending teams of inspectors to markets and stores to warn merchants of possible punishment if they refuse them.

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North Korea More Details About Coupons(https://mriguide.com/north-korea-more-details-about-coupons/)