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CD-57 →
Portable mechanical cipher machine

The HELL STG-61 1 was a small hand-held cipher machine, built in the around 1961 by Rudolf HELL in Kiel (Germany) for the post-war German Border Police (Bundesgrenzschutz, BGS) 2 as a replacement for the refusbished Enigma machines that were used until then. The STG-61 is one of two mechanical cipher machines, the other one being the H-54, that were built by HELL under license of the Hagelin Company in Switzerland. It is a purely mechanical machine, that can easily be hidden in the pocket of, say, a coat. It is compatible with the Hagelin CD-57 and the CX-52.

The machine is also interoperable with the HELL H-54 cipher machine that was built a few years earlier. The image on the right shows the STG-61, which closely resembles the Hagelin CD-57 and has identical dimensions. Although it is a functional clone of the CD-57, HELL managed to make a few improvements to the design.

The most obvious improvement over the original design is the presence of a thumbwheel to the left of the letter counter, allowing the counter to be reset easily without using the crank. On the CD-57 one had to write down the start position.
HELL STG-61 (Hagelin CD-57 clone)

The machine can be opened by pressing a small knob on top of the case. Inside, are two circular constructions: one below the alphabet disc, behaving like the cage of a H-54 or CX-52, and the other one in the form of a stack of six cipher wheels. These six cipher wheels are functionally identical to the pin-wheels of the H-54. Each disc has a different number of steps, using co-prime numbers to obtain the maximum possible cipher period. The following are present:

29 31 37 41 43 47

The number of steps in engraved in white on each disc. The wheel stack can be removed and the the wheels can be placed on the shaft in 120 different orders (6 x 5 x 4). For more information, please refer to our page about the Hagelin CD-57.

  1. STG = Spruchtarngerät (message disguise device)).
  2. The Bundesgrenzschuts (BGS) was the first federal police organization in Western Germany after WWII, permitted by the Allied authorities. In July 2005, the BGS was renamed Bundespolizei (Federal Police) [1].

Original packaging STG-61 HELL STG-61 (Hagelin CD-57 clone) The STG-61 in use The interior of the STG-61 Close-up of the coding wheels The counter Close-up of the character counter with the thumbwheel
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Original packaging
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HELL STG-61 (Hagelin CD-57 clone)
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The STG-61 in use
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The interior of the STG-61
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Close-up of the coding wheels
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The counter
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Close-up of the character counter with the thumbwheel

  1. Spruchtarngerät STG-61, Kurzanleitung
    CM-301013. CAG A-1150. Crypto AG, date unknown.
  1. Wikipedia, Bundesgrenzschutz
    Retrieved April 2013.
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Crypto Museum. Created: Saturday 24 July 2010. Last changed: Monday, 06 January 2020 - 11:44 CET.
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