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A rare, fully-functioning Enigma machine used by the Germans during World War Two has emerged for sale for £220,000. ($275,000)

This Enigma I model, made in Berlin in 1943, has three rotors, each with 26 positions, to create 17,576 possible combinations for each letter.

The Enigma was considered to be 'unbreakable', but the British codebreakers at Bletchley Park led by Alan Turing were famously able to decipher it.

In response to this alarming development, the Germans introduced a four rotor model which was even harder for the codebreakers to crack.