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G312
Abwehr Enigma stolen from Bletchley Park

Enigma G312 is an Enigma cipher machine model G31 — also known as a Zählwerksmaschine (counter machine) — manufactured around 1940 by Heimsoeth und Rinke in Berlin (Germany) for the German intelligence service — the Abwehr. The machine reached the headlines when it was stolen from its present location at the Bletchley Park Museum on 1 April 2000. It was recovered later that year, followed by the arrest of antiques dealer Dennis Yates from Derbishire (UK).

Shortly after the provisional opening of the Bletchley Park Museum, the machine had been given on loan by GCHQ and was on public display as part of a permanent exhibition [7].

At the time the museum was only open for two days on alternate weekends, when on Sunday 1 April 2000 the machine was taken from a display case in The Mansion in broad daylight. It reached the national news that night and was in the headlines of the newspapers the following day. It was reported as a unique machine of which only three were known, with a value of ~ £110,000.
  
Bletchley's G312

The theft was a great embarrassment for the Bletchley Park Trust and exposed the poor security measures at the museum at the time. Luckily, researcher David Hamer had recently written an article about the G312 for Cryptologia and had made several good quality photographs of it [3].

The machine was considered lost for several months until the police started receiving letters from a man claiming to act on behalf of some­one who had recently bought it. In the letters he demanded £25,000 for a safe return of the machine. Although the museum had agreed to pay the ransom, the 6 October deadline wasn't met and reportedly no money was payed [1].

Two weeks later the machine was sent to BBC reporter Jeremy Paxman, who received the parcel in his office at the London Television Centre.
  
BBC presenter Jeremy Paxman with the returned Enigma G312. Photo courtesy BBC News 2000 [5].

The machine appreared to be undamaged, but the three cipher wheels were missing. They were eventually returned safely at a later date. In November 2000, the British Police arrested 58-year-old Dennis Yates — an antiques dealer from Derbyshire. He admitted sending the ransom letters to the police and returning the machine to Jeremy Paxman, but insisted that he was acting on behalf of someone else. He refused to reveal the name of the person(s) involved in the theft, claiming that he had received death threats [1]. Somehow the situation ran out of his control.

Yates was subsequently sentenced to an imprisonment of ten months, but served less than three. Christine Large, the (then) director of the Bletchley Park Museum, later wrote a book based on the case, entitled Hijacking Enigma [5]. The theft of the machine was never solved and will probably remain a mystery, as Yates has meanwhile passed away. He was found dead in his car in 2017.

In 2004, Crypto Museum was permitted to take detailed photographs of the G312. 1

  1. The quality of the photographs of the Enigma G312 is somewhat sub-standard as they have been scanned from analogue negatives. At the time we didn't have a digital camera.

Enigma G at Bletchley Park
Close-up of Enigma G
David hamer (rear) and Marc Simons (front) discussing Enigma G
Marc Simons investigating the Enigma G-312
Wheels of the Enigma G-312
Enigma G entry wheel (ETW) and counter
Enigma G reflector (UKW)
Driving cog-wheel of the Enigma G
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Enigma G at Bletchley Park
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Close-up of Enigma G
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David hamer (rear) and Marc Simons (front) discussing Enigma G
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Marc Simons investigating the Enigma G-312
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Wheels of the Enigma G-312
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Enigma G entry wheel (ETW) and counter
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Enigma G reflector (UKW)
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Driving cog-wheel of the Enigma G

Wiring   G312
The table below shows the wiring of the G312. Although the machine is believed to have been used by the German Abwehr, it is the only one every found with this wiring. Different wirings were used for different sections of the Abwehr, and also for different radio nets. It is possible that some machines were rewired a number of times during their lifetime. Note the rewired UKW.

Wheel ABCDEFGHIJKLMNOPQRSTUVWXYZ Notch Turnover #
ETW QWERTZUIOASDFGHJKPYXCVBNML      
I DMTWSILRUYQNKFEJCAZBPGXOHV ACDEHIJKMNOQSTWXY SUVWZABCEFGIKLOPQ 17
II HQZGPJTMOBLNCIFDYAWVEUSRKX ABDGHIKLNOPSUVY STVYZACDFGHKMNQ 15
III UQNTLSZFMREHDPXKIBVYGJCWOA CEFIMNPSUVZ UWXAEFHKMNR 11
UKW RULQMZJSYGOCETKWDAHNBXPVIF      
 Other wirings


References
  1. BBC, 2000: Wartime coding machine stolen
    1 April 2005. Retrieved February 2013.

  2. Crypto Museum, Photographs of Enigma G-312
    Bletchley Park, August 2002, November 2004.

  3. David Hamer, G-312: An Abwehr Enigma
    Cryptologia, January 2000, Volume XXIV, Number 1.

  4. BBC, Photograph of Jeremy Paxman with Enigma G-312
    Copyright BBC News, 2000. Retrieved November 2005.

  5. Christine Large, Hijacking Enigma
    31 May 2004. ISBN 978-0470863473.

  6. David Kenyon and Frode Weierud, Enigma G: The Counter Enigma
    Bletchley Park and Crypto Cellar Research, 5 May 2019. Updated 15 June 2019.

  7. Mark Baldwin, The Stolen Enigma machine
    Website DR ENIGMA, 16 October 2017.
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Crypto Museum. Created: Tuesday 20 September 2022. Last changed: Friday, 07 July 2023 - 07:41 CET.
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