During WWII the British Armed Forces used several cipher systems for their low/mid level traffic, such as the Syllabic cipher, Slidex, Syko/Rekoh cards, Bomber code etc. Unfortunately it is difficult to find detailed information on these systems and how they were used during the war.
One of these systems was the SYKO hand operated device. This was used widely by the British Army and the RAF (including the planes of Coastal Command).
