London: Bletchley Park historians have recovered a rare machine used by Adolf Hitler to exchange top secret messages with his high command after finding it advertised on eBay for just £9.50 (Dh51).

Volunteers from the National Museum of Computing, based at the wartime code-breaking centre, tracked down the Lorenz teleprinter to a home in Southend, Essex, where it had been lying forgotten on the floor of a shed.

At first, the researchers assumed they had bought a civilian version of the machine, but when they discovered a swastika and unique military serial number they realised it was part of the system Hitler used to communicate with commanders such as Erwin Rommel. While the Enigma system was used by the German war machine to exchange coded messages with front-line units, the more complicated and cumbersome Lorenz coding system was used to deliver detailed messages exclusively to the eyes of the commanders at static headquarters.

Cracking the Lorenz code, which was achieved by Bletchley Park mathematician Bill Tutte, was one of the most significant British achievements of the war.

It enabled Gen Dwight Eisenhower to establish that the Allies’ decoy operation ahead of D-Day had fooled the Germans, as well as helping the USSR win the crucial Battle of Kursk.

Only 200 of the teleprinters, each of which accompanied a cipher coding machine, were ever manufactured and historians believe the vast majority were destroyed at the end of the war. John Wetter, a volunteer engineer at the National Museum of Computing, described the moment he realised the Lorenz teleprinter was part of Nazi high command apparatus. “We saw the swastika and then we noticed one of the keys was devoted to the double lightning bolt symbol of the SS,” he said. “We’d simply never seen one before. “It does make you wonder what kind of messages were sent and received on that particular machine, I must admit.” In recognition of the D-Day anniversary next month, the machine is being united with a Lorenz cipher unit, on loan from Norway’s Armed Forces. The National Museum of Computing has now appealed for help finding the system’s only missing component, the electric motor. “That will give us the chance to show the breaking of the Lorenz cipher code from start to finish,” said Andy Clark, the museum’s chairman.