Intended for high-level encryption, the Japanese family of machines using telephone selector switches came to be known in the United States by their 'color' code names: Coral, Jade, and Purple. The switches performed the same function as a wired rotor, stepping forward through each of the 25 contacts. However, unlike wired rotors, the switches could not be taken out and rearranged, a serious limitation to the system. The Japanese Imperial Navy used the Jade machines for its high-level encryption of the katakana syllabary. The Japanese diplomatic system, code named Purple, differed from Jade in that it included a plug board.
Also, on display is the Army's first analog machine used to decrypt Purple enciphered messages. This machine solved the famous 14-part message telling the Japanese ambassador to break relations with the United States on December 7, 1941, at 1:00 p.m.