The German Development through the SG-41
Schlüsselgerät 41 (cipher machine 41), or SG-41, was a mechanical pin-wheel cipher machine that was developed during WWII by Regierungsoberinspektor Fritz Menzer as a possible replacement for the (Abwehr) Enigma machine.
It was manufactured by Wanderer Werke in Chemnitz (Germany) and was introduced on 12 October 1944.
Although 11,000 units were ordered, only between 1000 and 2000 units had actually been delivered by the end of the war.
The machine is also known as Hitlermühle (Hitler Mill) because of the large crank at the right.
The machine is not based on the rather common principle of the rotor machine, like the Enigma, but on the pin-and-lug principle of the C-machines, developed by Boris Hagelin in Sweden.
Similar systems were developed by Hagelin before the war (e.g. the C-38) and were used during the war by the American Army (M-209).
LAlthough the SG-41 is clearly based on the C-38/M-209, it has been improved in a number of areas.
In particular, it features very irregular wheel movements and wheel stepping in both directions, making it very difficult to break.
The image on the right shows a typical SG-41 machine that is in the collection of GCHQ.
The machine shown here is the alphanumerical variant with 26 letters on the keyboard (A-Z).
The letter J is marked in red, probably as it is used to shift between letters and numbers.
When in storage, the machine is normally protected against dust and damage by a rectangular cover.
Photograph Crown Copyright. Kindly supplied by GCHQ.
According to the serial number plate that is mounted at the rear, the machine shown here has serial number 000460 and was manufactured in 1944 by Wanderer-Werke AG (manufacturer code CXO) in Siegmar-Schönau.
At the time, Wanderer was one of the leading manufacturers of typewriters in Germany. At the outbreak of the war, Siegmar-Schönau was a rather large industrial city in east Germany. Today, the former city is a suburb of Chemnitz (Germany).
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