An Enigma machine, used by Germany to send encrypted communications during World War II, has been sold at auction in London. The machine, which was constructed in 1943, is one of few that survived the conflict intact, as the German military was given orders to destroy them as it retreated.

During its years of use, the German military altered and refined the Enigma cipher machine, creating numerous different models. The 1943 example included three rotors, and was sold complete with an oak hinged-lid carrying case.

The final sale price of the machine was £149,000 (US$232,015), significantly more than the expected £50,00-70,000 ($78,000-109,000) figure. It was purchased by an unnamed buyer. Given the historical significance of the machine (it was originally invented in 1918), the high sale price of auctioned example is really no surprise.

To use Enigma, the operator would type in a message, then scramble it using three, four or five notched rotors, each with 26 possible positions. Whoever received the message needed to know the exact settings of the rotors, and those of the machine's plugboard, in order to decode the message. There were more than 159 million million million possible configurations (that's not a typo), and the settings were changed daily.

During the Second World War, the German military believed that the encryption granted by Enigma could not be broken, but thanks to a combination of Polish intelligence and the work of codebreakers at Bletchley Park – including mathematicians Gordon Welchman and Alan Turing – the cipher was eventually beaten. They employed the use of huge, one-ton code-breaking machines called British Bombes, more than 200 of which were used during the height of the operation.

The wartime efforts of the men and women at Blethchley Park – and Alan Turing in particular – were recently dramatized in The Imitation Game, which helped to highlight the importance of the work to modern generations. Like the rare Enigma machine sold at Sotheby's, Alan Turing's handwritten notes on the project, contained within a 56-page notebook, were also recently auctioned by Bonhams Fine Books & Manuscripts in New York.

If you're interested in reading more about the history surrounding the astonishing machine and the men and women who worked against it, you can check out our feature on the extraordinary wartime contribution that came out of an unassuming mansion in Buckinghamshire, UK.

Source: Sotheby's

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