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HELL STG-61
Portable mechanical cipher machine

The HELL STG-61 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) 1 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.
  
Typical view of the STB-61 with the handle in the extended position

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 functional 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. 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 Typical view of the STG-61 Typical view of the STB-61 with the handle in the extended position 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

 
References
  1. Wikipedia, Bundesgrenzschutz
    Retrieved April 2013.

Further information

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