More advanced than the Enigma, the British Portex cipher machine used irregular stepping and eight rotors. Similar to ‘Caesar slide’, a simple letter substitution code used by Roman general Julius Caesar, the wheel used to input the letter to be encrypted, could be set with an initial offset of its alphabet. As an ‘offline’ system, it printed a stream of cipher that was then separately typed into a teleprinter system for transmission or sent using Morse code. These two features are similar to those found on the Hagelin pinwheel machine, the M209. The Portex can be regarded as a hybrid of the M209 and the electro-mechanical Enigma.
The Allies used the M209 from the 1940s to mid-1950s to protect military messages. Other countries used variants to support government services.
Portex - ASD Records
M209 - ASD Records