An “unbreakable” cipher machine used to encrypt massages from the Nazi command, which led to huge breakthroughs in modern computing has been discovered for sale on eBay for less than £10.

A volunteer with the National Museum of Computing (NMC) spotted the advert on the online auctioning site this week and recognised the device, labelled a “telegram machine”, as an extremely rare, military-issue Lorenz teleprinter.

John Whetter, a volunteer engineer with the NMC, told the Guardian: “I think it was described as a telegram machine, but we recognised it as a Lorenz teleprinter.”

The museum tracked down the seller in Essex, who showed them the rare keyboard buried under rubbish in a garden shed in its original carry case.

"We said 'Thank you very much, how much was it again?' She said '£9.50', so we said 'Here's a £10 note - keep the change!'” Mr Wetter told the BBC.

Women during WW II: teleprinter operators for the German Wehrmacht (Getty ) (Getty)

Upon cleaning the machine at Bletchley Park, the museum found swastika detailing on the device as well as a special key for the runic Waffen-SS insignia.

After serendipitously finding the component and receiving a long-term loan of the Lorenz SZ42 cipher machine from the Norwegian Armed Forces Museum in Oslo, the NMC is now looking for the final parts of the contraption to restore the encoder to working order.

The NMC are encouraging people to comb their sheds and attics for a missing drive motor so they can recreate the process of top secret transmissions from encrypt to decrypt using the full set of 1940’s cutting edge technology.

Nazi gold hoard uncovered

“To do that we have to replace some missing components, in particular the drive motor – and it’s the drive motor that’s our next quest,” said Mr Whetter.

More complex than the famous Enigma machine, the Lorenz cipher was only able to be broken due to Bill Tutte’s judgements about the workings of the Lorenz machine, despite never having laid eyes on one of the devices.

Consequently, the Allies were regularly able to read the German High Command’s top secret messages. From 1944, with the creation of the Colossus computer by Tommy Flowers, a Post Office engineer, the Allies were able to reduce the decryption time from weeks to hours, undermining the German military machine.

New online database lists Nazi loot for repatriation Show all 7 1 /7 New online database lists Nazi loot for repatriation New online database lists Nazi loot for repatriation In this April 12, 1945 photo released by the U.S. National Archives, U.S. Gen. Dwight D. Eisenhower, Supreme Allied Commander, accompanied by Gen. Omar N. Bradley, left, and Lt. George S. Patton, Jr., inspects art treasures stolen by Germans in a salt mine in Merkers, Germany. Holocaust survivors and their relatives, as well as art collectors and museums, can go online beginning Monday, Oct. 18, 2010 to search a historical database of more than 20,000 art objects stolen in German-occupied France and Belgium from 1940 to 1944. AP New online database lists Nazi loot for repatriation In this May 13, 1945 photo released by the U.S. National Archives, "The Graces in the Gardens of the Hesperides" by Peter Paul Rubens painting taken by the Einsatzstab Reichsleiter Rosenberg (ERR), is shown. Holocaust survivors and their relatives, as well as art collectors and museums, can go online beginning Monday, Oct. 18, 2010 to search a historical database of more than 20,000 art objects stolen in German-occupied France and Belgium from 1940 to 1944. AP New online database lists Nazi loot for repatriation In this May 13, 1945 photo released by the U.S. National Archives, the Alfred Rosenberg Einsatzstab Reichsleiter Rosenberg (ERR) files are shown in a room of the Neuschwanstein Castle in Germany, where the largest Nazi art loot cache was found by the U.S. Army when they explored tunnels under the castle. Holocaust survivors and their relatives, as well as art collectors and museums, can go online beginning Monday, Oct. 18, 2010 to search a historical database of more than 20,000 art objects stolen in German-occupied France and Belgium from 1940 to 1944. AP New online database lists Nazi loot for repatriation In this May 13, 1945 photo released by the U.S. National Archives, U.S. Army Sgt. Harold Maus of Scranton, Pa., looks over an engraving by German artist Albrecht Durer, which was found among other art treasures at a salt mine in Merkers, Germany. Holocaust survivors and their relatives, as well as art collectors and museums, can go online beginning Monday, Oct. 18, 2010 to search a historical database of more than 20,000 art objects stolen in German-occupied France and Belgium from 1940 to 1944. AP New online database lists Nazi loot for repatriation In this April 24, 1945 photo released by the U.S. National Archives, an American soldier stands among German loot stored in a church at Elligen, Germany. Holocaust survivors and their relatives, as well as art collectors and museums, can go online beginning Monday, Oct. 18, 2010 to search a historical database of more than 20,000 art objects stolen in German-occupied France and Belgium from 1940 to 1944. AP New online database lists Nazi loot for repatriation In this April 25, 1945 image released by the U.S. National Archives, U.S. Army personnel stand by a painting called, "Wintergarden," by French impressionist Edouard Manet, which was discovered in the vault in Merkers, Germany. Holocaust survivors and their relatives, as well as art collectors and museums, can go online beginning Monday, Oct. 18, 2010 to search a historical database of more than 20,000 art objects stolen in German-occupied France and Belgium from 1940 to 1944. AP New online database lists Nazi loot for repatriation In this Feb. 4, 1997 file photo, Dr. Willi Korte, center, and Christoph von Berg, representing the Kunstsammlungen zu Weimar, examine "Portrait of Elizabeth Hervey Holding a Dove," a 1778 painting by Johann Friedrich August Tischbein that was looted from the German museum at the end of World War II, at Sotheby's auction house in New York. Korte has been at the forefront of the worldwide search for art looted by the Nazis, an undertaking that has accelerated over the past two decades, spurring court battles and putting the descendants of Jewish families that were forced to give up their possession against museums and private collectors. AP

An estimated 200 Lorenz machines were in existence during World War II, but only four are known to have survived.