They did it for a 3 year period from 2002-2005. https://en.m.wikipedia.org/wiki/North_Korea%E2%80%93United_States_relations#:~:text=In%20September%202005%2C%20

They did it for a 3 year period from 2002-2005. https://en.m.wikipedia.org/wiki/North_Korea%E2%80%93United_States_relations#:~:text=In%20September%202005%2C%20the%20US,produce%20such%20high%2Dquality%20notes https://en.m.wikipedia.org/wiki/North_Korea%E2%80%93United_S....