On November 9, 1963, two investigators from France’s Central Office for Counterfeit Currency Control (OCRFM) arrived at the post office on Rue Turgot in Paris’s 9th arrondissement. Five days earlier, a customer had purchased 1,000 francs’ worth of Treasury bonds there using a stack of crisp 100-franc notes bearing the portrait of Napoleon Bonaparte. At first glance, nothing seemed unusual. The notes looked authentic, felt authentic, and even carried convincing watermarks. But they were counterfeit.

A 'Bonaparte' 100 Franc notes that Ceslaw Bojarski forged. Credit: Wikimedia Commons