Lot 67
  • 67


350,000 - 500,000 USD
Log in to view results
bidding is closed


  • A fully operational four-rotor ("M4") Kriegsmarine Enigma Cipher Machine. Berlin-Wilmersdorf, Germany, Heimsoeth und Rinke, 1944.
  • aluminum, glass, power source
Four-rotor ("M4") Kriegsmarine Enigma cipher machine, serial number M77772, complete with Gamma rotor (M6927), 3 aluminum rotors (I, II, & V) with matching serial numbers (M8264), and C reflector (M18345), each rotor with 26 positions labeled with letters. Housed in the original oak case with metal handle (13½ X 11 X 6¼ in.), hinged front panel opening to reveal ebonite Steckerbrett [plug-board], outside of case and inside of lid with matching metal plates reading "M 7772." Control panel with standard raised "QWERTZ" keyboard of 26 Bakelite keys in white on black backgrounds, lockable rotor cover, battery compartment and 4V power socket, keyboard with manufacturer's metal label reading "M77772/JLA/44," removable light panel with letters A-Z lifting to reveal 26 light bulbs, Steckerbrett with 12 original patch cables (8 plugged into the Steckerbrett and 4 stored in lid of case), lid with 10 spare bulbs, green contrast filter, spare patch cables, and original paper instruction label with serial number in manuscript. WITH: Original German naval telegraph key, and two facsimile user manuals.


A very fine, fully operational M4 Enigma with serial number M77772, complete with Gamma rotor (M6927), 3 aluminum rotors (I, II, & V) with matching serial numbers (M8264), and C reflector (M18345), full complement of patch/stecker cables, wear to case consistent with use. Machine has been fitted to be powered by three modern AA batteries. Complete with original naval telegraphy key, and facsimile manual.
In response to your inquiry, we are pleased to provide you with a general report of the condition of the property described above. Since we are not professional conservators or restorers, we urge you to consult with a restorer or conservator of your choice who will be better able to provide a detailed, professional report. Prospective buyers should inspect each lot to satisfy themselves as to condition and must understand that any statement made by Sotheby's is merely a subjective qualified opinion.

Catalogue Note

A VERY FINE AND FULLY OPERATIONAL EXAMPLE OF THE FAMOUS GERMAN FOUR-ROTOR ("M4") KRIEGSMARINE ENIGMA CIPHER MACHINE. THE RAREST AND MOST DESIRABLE OF ALL ENIGMAS, THE M4 WAS ONE OF THE HARDEST TO DECRYPT. VERY FEW M4 MACHINES SURVIVED THE WAR, AND TO FIND ONE THAT IT COMPLETE AND STILL IN SUCH PRISTINE CONDITION, FULLY OPERATIONAL IS RARE INDEED. The M4 Enigma machine was an electromechanical cipher machine specifically developed for use by the U-boat division of the German Navy (Kriegsmarine) for communication with the naval bases, where it played a pivotal role in the Battle of the Atlantic. Admiral Karl Dönitz, the commander of the U-boat fleet seriously doubted the security of the Enigma after several unexplained losses, and had the secret M4 model developed specifically for his fleet. The M4 was ready around May of 1941, and by February of 1942 all M4 machines had been distributed with the new operating procedures placed into effect. 

While the codebreakers at Bletchley had been reading messages encrypted by the 3-Rotor machines for some time, the introduction of the M4 caught them completely off-guard, shutting them completely out, and it took them a full 9 months to catch up and solve the new code. Few Enigma machines survived the War intact: the Germans destroyed them as they retreated, and for decades after the war governments around the world kept close control over Enigma technology (indeed two of Turing's wartime papers on cryptography remained classified until 2012). So secure was the system believed to be that some governments, unaware of the work of Bletchley Park, continued to use Enigmas after 1945.

The M4 was a variation of the 3-rotor Enigma I machine used by the Wehrmacht (German Army & Airforce). It accepted 3 standard rotors and a narrow fourth rotor in combination with a narrow reflector. The two narrow components allowed all four rotors to fit into a modified three-rotor Enigma chassis. It was issued with eight standard rotors, the first five having wiring identical to the rotors issued with the three-rotor Enigma-I. Two narrow fourth rotors, Beta and Gamma, were also issued with each machine. With the fourth narrow rotor in the "A" position, the M4 became functionally identical to and could communicate with the three-rotor Enigmas used by other branches of the military. With its stricter operating procedures and the ability to select from among 8 standard rotors and two thin fourth rotors gave the M4 a much higher level of security, foiling the Allies' previously successful decryption of the U-boat signals. It would take the codebreakers at Bletchley 10 months to break the new encryption. Compared with the more common 3-rotor Enigma, the M4 had many significant differences beyond the added rotors. It had a different ring-setting mechanism on the rotors, a lockable rotor cover to keep the wheel settings secret, a removable lamp panel which allowed for the inclusion of a printer (Schreibmax), a power socket for an external power source, and a metal handle instead of the more fragile leather handle found on the 3-rotor machines. The M4 also had a removable top, and two metal bracket that allowed the machines to be lifted out of the compartments in the U-boat radio rooms. 

M4 Enigma machines were produced in much smaller quantities than the three-rotor Enigma I machines. In addition, multiple M4 Enigmas were deployed with each U-boat and support ship, and the majority of these were lost when their boats were sunk in combat or scuttled by their crew at the end of the war. Furthermore, German Enigma operators were under strict orders not to allow the enemy to capture any Enigmas; this meant that many Enigmas were stripped of their rotors and destroyed, with many thrown into lakes or oceans to hide any remaining parts.