41. Notes on the chassis of the Bombe by Phil Bochicchio, undated, "Bombe" files of the National Cryptologic Museum.

42. E.C.M. expands to Electromechanical Cipher Machine. An identical machine was used in the U.S. Army and was known as SIGABA (which doesn't expand to anything).

43. Bombe History, 10.

44. The U.S. Army also had a Bombe project, but it was not built to deal with the U-boats' four-rotor messages. For a brief description of the Army machine, see Appendix II. 45. Memorandum from OP-20-G, "Brief Resume of Op-20-G and British Activities vis-a-vis German Machine Ciphers," July 15,1944, 3.

46. Bombe History, 9. However, the memo "Brief Resume of Op-20-G and British Activities vis-a-vis German Machine Ciphers," 3, cites the figure as 40 percent naval and the remaining 60 percent on German Army and Air Force. The memo is dated only six weeks after the Bombe History, so it is possible the efficiency improved.

47. Memorandum from OP-20-G, "Contract NXs-7892 - Curtailment of," September 8,1944.

48. Cummings, James, "A Salute to the Waves," Dayton Daily News, September 10,1995, City p. 1E.