An early Naval Enigma model (the "O Bar" machine) had been solved before 1931 by the Polish Cipher Bureau, but it did not have the plugboard of the later standard Enigma. Mahon (1945) cites, as his source for "most of the information I have collected about prewar days", Alan Turing, who had received it from the "Polish cryptographers", who Mahon says had done "nearly all the early work on German Naval Enigma [and] handed over the details of their very considerable achievements just before the outbreak of war."[24] Mahon, A. P. (June 1945), The History of Hut Eight: 1939–1945, archived from the original on 7 March 2016, retrieved 12 February 2019, 117 pp., PRO HW 25/2
Lawrence (2004) shows how Rejewski could have adapted his method to solve for the second rotor, even if the settings lists had not straddled the quarterly changeover period. Lawrence, John (April 2004), "The Versatility of Rejewski's Method: Solving for the Wiring of the Second Rotor", Cryptologia, 28 (2): 149–152, doi:10.1080/0161-110491892836, S2CID205486319
Lawrence (2004) shows how Rejewski could have adapted his method to solve for the second rotor, even if the settings lists had not straddled the quarterly changeover period. Lawrence, John (April 2004), "The Versatility of Rejewski's Method: Solving for the Wiring of the Second Rotor", Cryptologia, 28 (2): 149–152, doi:10.1080/0161-110491892836, S2CID205486319
An early Naval Enigma model (the "O Bar" machine) had been solved before 1931 by the Polish Cipher Bureau, but it did not have the plugboard of the later standard Enigma. Mahon (1945) cites, as his source for "most of the information I have collected about prewar days", Alan Turing, who had received it from the "Polish cryptographers", who Mahon says had done "nearly all the early work on German Naval Enigma [and] handed over the details of their very considerable achievements just before the outbreak of war."[24] Mahon, A. P. (June 1945), The History of Hut Eight: 1939–1945, archived from the original on 7 March 2016, retrieved 12 February 2019, 117 pp., PRO HW 25/2
Farago 1971, p.674Farago, Ladislas (1971), The Game of the Foxes: The Untold Story of German Espionage in the United States and Great Britain during World War II, New York: Bantam Books, OCLC2371136
