This machine, constructed in 1940 by US cryptanalysts, was used to read 'Purple', the Japanese diplomatic code (not, it should be noted, the Japanese naval code). Purple offered millions of cipher combinations. The Japanese considered the system unbreakable, but they made the mistake of phasing it in gradually while still employing the previous 'Red' code, which US intelligence had been reading for some time. The overlap helped US cryptanalysts break the Purple code and reproduce the machine, which employed telephone stepping switches rather than the more traditional rotor system. The cryptanalysts were hailed as 'magicians', and the intelligence derived from reading Purple was known as 'Magic'.
