This paper describes the exact operation of Schlüsselgerät 41 (cipher machine 41), also known as SG-41 and Hitlermühle, and explains the complex order and timing of the events that take place when a text is enciphered. The authors believe that this is the first time that some of the properties of this machine are revealed. A comparison is made with the contemporary and similar Hagelin M-209 and BC-38 machines, and it is shown that the SG-41 was more advanced in several ways.

While the C-52 and CX-52 devices enter the open market and are exhibited in museums, it is hard to the untrained eye to tell the differences. There is a lot of confusion, and half-truths muddle the waters even further. It turns out that there is only a limited number of standard configurations of the C-52 and CX-52 machines. These 'models' are described in detail, to enable the reader to identify machines he/she comes across. All the configurable components are described, to aid in the understanding of their differences and of the way the devices work.