Catalogue description Special Operations Executive: Playfair and Wireless Operators Codes Nominal Card Index

This series contains the nominal Playfair code card index showing code details for each agent or wireless operator in the field. The Playfair code (invented by one of the devisers of the telegraph, Sir Charles Wheatstone) was that used by SOE agents up to 1942, when its weaknesses were demonstrated by Leo Marks and the code was progressively replaced by more secure coding practices.

For each agent, the index card shows the letter square to be used and the phrase it was derived from, along with the various security measures agents were to apply to their messages sent from the field. The cards include a date of which the meaning is now not clear, but which may be the date of the agent being trained in the use of the code.

Foreign Office, Special Operations Executive, 1945-1946

Ministry of Economic Warfare, Special Operations Executive, 1940-1945

In 2004 Secret Intelligence Service