The toolmaker and later cryptologist Fritz Menzer headed the encryption department of the Wehrmacht High Command. Numerous inventions were made by him, such as the cryptographically extremely secure cipher box and the SG-41 cipher device, but were too late in production for the war. Some interesting details about this largely unknown inventor could already be taken from TICOM documents, German archives and from personal interviews with relatives.

(TICOM =  the Target Intelligence Committee (U.S.A. and U.K.), conducted interviews and investigations with prisoners of war immediately after the end of the war and recorded them in TICOM documents; since 2011, most of them have been released by the NSA as so-called ‟declassified documents”. )

Although the basic operation of the Schlüsselgerät 41 is known, it has up until now not been possible to understand every detail and simulate the encryption algorithm due to a lack of design drawings or intact devices. For this reason, as part of the 3D Cipher study of the Deutsches Museum, CT scan data will be produced of both our devices and of a fully functional device of a private collector, in order to finally fully understand the algorithm.

Thus this machine remained imprecisely documented and was estimated by the curator at the time to be constructed in 1876 – a date that did not seem to be consistent. Meanwhile, research conducted in Denmark by various institutions, archives and experts revealed that our cryptograph was probably made around 1890 at Professor E. Jünger’s “Mechanical Etablissement” in Copenhagen, a highly respected company with which Köhl had a good working relationship.