Footnotes

Enigma has its origins in a series of cipher machines developed by German engineer Arthur Scherbius in the immediate period following the First World War. Initially aimed at the commercial market, it was adopted, most notably, by the German armed forces.

Various models were developed in the years leading up to and during the Second World War, with specific models and wiring configurations used by the Army (Heer) and Airforce (Luftwaffe), Navy (Kriegsmarine), Railways (Reichsbahn), Intelligence (Abwehr), etc.

Admiral Dönitz of the Kriegsmarine, concerned about the security of Enigma, ordered the development of the M4 in 1941. The M4 differs from other models in that it has a fourth, additional but non-rotating and non-interchangeable rotor that increased the complexity of the enciphering process It was the fourth naval model and was particularly intended for use by the U-boat division. Production of this model began in late 1941 and it was introduced early into 1942.

With the increased complexity introduced by this model, the M4 came as a shock to Allied codebreakers and went unbroken for nine months, until the capture of important key sheets aboard the U-559 by British sailors in October 1942. Traffic enciphered by the M4 was codenamed SHARK by Allied codebreakers and this eventual breach of this communications channel played an important role in the Battle of the Atlantic.

The German High Command ordered that Enigma machines be destroyed in the event that capture by Allied forces was imminent, so few survive today. The M4 is rarer than its Army counterpart, the Enigma I, with just 70-80 surviving examples of the M4 recorded worldwide, of which only about half are in private hands. The M4 offered by Bonhams is a very fine, well-preserved example.

For further information about the M4 Enigma see www.cryptomuseum.com/crypto/enigma/m4/

Provenance:
Property of a Norwegian private collector.