A German Naval 4-rotor Enigma enciphering machine (M4), for U-Boat use, circa 1942-44.

An operational M4 Enigma machine, for use exclusively on the U-Boat fleet, serial number No. M 17158, as stamped on the bed-plate, and aluminium rotors I, IV and VII, and a bakerlite Beta rotor and reflector, all with matching numbers M17158, lamp-board display, standard QWERTY keyboard of 26 keys, white on black, battery switch, ebonite steckerbrett (plugboard), with 4 cables, the outer case lid with 4 spare cables, a colored glare screen, printed instructions in German, and a set of spare bulbs. The keyboard and rotors set in a black crackle finish metal case, the machine in an oak outer case with metal lock and carrying handle.



A fully operational M4 enigma machine, one of the rarest of all the enigma machines, in fine condition. The legendary German encrypting machine was used by the Navy, ordered by Doenitz in late 1941, as he suspected (rightly) that the Naval 3 rotor machine had been compromised with the capture of U-570 in August 1941. He ordered it specifically for the use of the growing U-Boat fleet, which Germany required to take the war to the Allies in the Atlantic. For this campaign, the Naval High Command needed to know, on a daily basis, the positions of the U-Boats and the vessels needed to receive orders as to where they were to go, and all this information had to be secure. After February 1942 when the M4 became operational, perhaps some 500 U Boats were constructed, and as the machines were also replaced in the earlier submarines, it is likely that from 1942, 700 to 800 submarines were equipped, most with two M4s each (they needed the two machines with the two settings around midnight when the changeover of coding occurred). This would make a total production of probably just over 1600 machines. Since over 80% of all u-boats were sunk in World War II, the survival rate was particularly low, and of course Captains had strict orders to smash their machines when captured. We know the Allies, in late 1945 and early 1946, assembled the majority of the 'Allied captured' 154 U-Boats in Lisahally, N. Ireland, and in Loch Ryan, Scotland. There 121 of the the submarines were stripped, and scuttled in deep water. The Danish, Dutch, and French also had a few U-boats, and the Danish sold two of theirs to the Israelis.



The numbers of surviving M4s, given that at least 70% of commanders should have destroyed their machines before surrendering, can be estimated at 120 examples extant, mostly one suspects, languishing in Government storerooms around the world. The M4s, all came directly into the hands of the Allied Naval Forces after the war, whether it be in Britain, France, Australia, US, Denmark or Holland, and were not allowed to slip out of military control. The US/British forces rounded up as many M3 (army) machines as they could from the surrendering German Forces and many of them were sold back to the Eastern Bloc on a clandestine basis, which allowed the Allies to listen in to military orders throughout the Cold War. Of the surviving M4s it is suspected that for every 10 M3s there might be one M4. Analysis of the 24 Museums around the world show a total of circa 50 Enigma machines on display, of which 7 are M4s, taken from captured U-Boats. Of the many M3s, most languish in government storerooms, some 50 were found in Madrid in 2008, used by Francos regime up until the 1950s.



The story of the Enigma starts in WWI, when the British were intercepting and reading all the German Navy signals. The enigma was patented by Artur Scherbus in 1918 but it was not until 1926 that the code breaking of the WWI signals was discovered by the German High Command, and the Enigma became their encyphering machine of choice. The early enigmas had 3 interchangeable rotors, which scrambled plain-text messages and produce a cipher text message, which is sent via Morse code to a receiver machine with the same settings. The Allies breaking of the Enigma codes was one of the breakthroughs of the War..it started when Polish cryptgraphers passed on to the British their research on the codes in 1937, and in 1939 the French captured a submarine with a codebook. There was also information retrieved by a spy in Germany. The outcome was that the 3 rotor code was broken early on in the war by the code breakers at Bletchley Park set up in 1937, and included Turing, Foss, Knox and many others. In all some 12,000 people worked at Bletchley Park during the war and Churchill ordered the destruction of all paperwork and machinery, soon after the war. When the M4 came into use on 1st February 1942 it took over 9 months to crack that code, assisted by the capture of codebooks from U-599 in October 1942. Various other devices were added to the M4 from 1944, notably a UKW-D, a field rewireabkle refractor to replace the reflector and extra wheel. It is one of the rarest of Enigma machines.

Wooden case: 12 x 10 x 5in (30.5 x 25.5 x 12.5cm)

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