This four-wheel Enigma machine was used by the German forces during the second world war to send coded messages.
Many machines of this type were used on the U-Boat submarines sent out to disrupt allied shipping and two were also housed at the German Naval Signals Bunker at St Jacques in St Peter Port, Guernsey during that island's occupation from 1940-1945.
A massive staff of boffins at Bletchley Park in Buckinghamshire ensured that the messages sent via these machines - once intercepted - could be read and understood by British forces. However it was essential to allied interests that the German operators go on believing they were secure. The curator and owner of the German Occupation Museum, Richard Heaume, told BBC Guernsey the success of that deception had a lasting impact:
"The German Naval officer in charge of signals in Guernsey, Oberleutnant Hagedorn, when he came to give a lecture in Guernsey in 1980 did not believe that his codes had been deciphered even then."
The Bletchley Park site is now a famous visitor attraction but was one of the best kept secrets of World War II and has only become popularly known in the last few decades.