The Christian Science Monitor has an opinion piece by John K. Cooley that provides an overview of the counterfeiting of US currency by North Korea.

Back in 1976, Pyongyang purchased from a specialized Swiss firm a sophisticated intaglio (high-pressure) press for printing currency. At the time, it was identical to the presses used by the US Treasury’s Bureau of Engraving and Printing to turn out hundreds of millions of dollars in genuine greenbacks annually (and is thought to be still highly similar).

After nearly a decade’s delay, high-quality counterfeit intaglio-printed $100 bank notes with only microscopic flaws – dubbed “Supernotes” by bankers and currency buffs – were spotted and seized, first in the Philippines, then in Hong Kong, Thailand, and finally, in the early-1990s, in Europe and the Americas.

North Korea is estimated to have earned $20 Million in the counterfeiting of US currency.