filed 1921-03-24 — "Apparatus for Ciphering and Deciphering Code Expressions", filed 1922-03-25. Implemented in A-4. Swedish patent SE59906, filed 1921-03-02, — "Apparatus for the Production of Cipher Documents Especially For Telegraphic Dispatch", filed 1922-03-01. Implemented in B-1. Swedish patent SE61104 filed 1923-09-28, — "Apparatus for Producing a Series of Signs", filed 1924-09-25. Implemented in A-22. Swedish patent SE65901, filed 1924-06-27 — "Electric Apparatus", filed 1925-08-31.Implemented in B-13. References Sources Beckman, Bengt. Codebreakers: Arne Beurling and the Swedish crypto program during World War II, p. 17-19. Kahn, David. The Codebreakers, 1967, 2nd edition 1996, Chapter 13. McKay, C.G. and Beckman, Bengt. Swedish signal intelligence 1900-1945. Frank Cass, London 2003. p 25-28. Further reading Original documents can be found at two main sources: ”Svartlösa och Öknebo häradsrätt” 1921-22. Stadsarkivet, Stockholm. Court protocols containing information about Damm´s private life (in Swedish). Boris Hagelin´s archive. Krigsarkivet, Stockholm. 55 volumes of which 15 contain documentation about Damm and the Cryptograph company from the years 1916-1930. Boris Hagelin´s memoirs exists in three versions. Comparison with original documents from Cryptograph shows many errors. The “Hauszeitung” from 1992 is the best. The English “The story of the Hagelin cryptos” has more errors than the German “Die Geschichte der Hagelin Cryptos”. See also Edward Hebern Arthur Scherbius 1869 births 1928 deaths Cipher-machine cryptographers 20th-century Swedish engineers 20th-century Swedish inventors Swedish cryptographers