In the German Army and Air Force Enigma, the reflector was fixed and did not rotate; there were four versions. The original version was marked 'A', and was replaced by "Umkehrwalze B" on 1 November 1937. A third version, "Umkehrwalze C" was used briefly in 1940, possibly by mistake, and was solved by Hut 6. The fourth version, first observed on 2 January 1944, had a rewireable reflector, called "Umkehrwalze D", nick-named Uncle Dick by the British, allowing the Enigma operator to alter the connections as part of the key settings.