Siemens and Halske T52e Cipher Machine, known as "Geheimschreiber" Serial No.43996
Geheimschreiber: German secret writing machine, 1940s
This cipher machine was used by German High Command for highly secret messages. The teleprinter machine automatically printed out the message as it was decrypted.
British code-breakers at Bletchley Park referred to these machines and the messages they encrypted as STURGEON. They did break this cipher, but not as easily or as often as less complex German military cipher systems.
Unlike Enigma or Lorenz messages, which were sent by radio, the Geheimschreiber was used over land lines and so could not be easily intercepted.