Indiana University-Purdue University Fort Wayne
During WWII, prisoners at the Sachsenhausen concentration camp were tasked with producing high quality counterfeit British and American currency. The plan was to produce a huge quantity of notes that would be released into the respective economies in an attempt to undermine the Allied war effort. Meanwhile, the British had similar plans for the Reichsmark.
Garret Marshall (2011).
Operation Bernhard, Macroeconomic Effects of Counterfeit Currency.