On a genuine $100 bill, a line at the base of the lamppost near Independence Hall is printed weakly. In the late 1980s investigators found counterfeit hundreds on which that line was flawless. These were superdollars, or supernotes: fakes on the same 75 percent cotton, 25 percent linen stock as real currency, printed by the intaglio process with raised ink, and carrying magnetic signatures that satisfied bank scanners. Experts identified 19 versions over the years, each fixing earlier weaknesses. Journalist Klaus Bender argued that the tiny remaining differences were deliberate marks that let the makers recognize their own product.

This episode works through the question of who had the means to run what amounted to a parallel mint. A 2002 sting in Manchester, England broke a syndicate holding $3.5 million in fake US cash, but investigators concluded such gangs were distributors, not the source. Washington named North Korea, alleging about $45 million produced since 1989 under the secretive Room 39. Others doubted it, including South Korea, the Swiss Federal Police, and an audit of the Macau bank the United States blacklisted. Rival theories point to Iran, Syria, and even the CIA.

• Telltale signs include clock hands on Independence Hall that stop short of the inner circle and a microscopic extra slash beside the letter N in United States.
• The Manchester gang was recorded boasting it could print half a million fake dollars a day, and the Bank of England admitted its fake ten pound notes were of excellent quality.
• Defectors claimed North Korean diplomats passing through Moscow received travel cash that was half genuine and half counterfeit, often without knowing it.
• U.S. indictments alleged that Sean Garland of the Official IRA moved bulk supernotes from Moscow into Dublin and Birmingham. The Irish High Court dismissed his extradition in 2011.
• The 2013 redesigned $100 bill answered with a woven blue 3D ribbon of microscopic lenses and color-shifting ink that intaglio presses cannot reproduce.