Hand-held cylinder, used by the U.S. Army from 1934 through World War II, that permitted simple enciphering of messages. Based on the concept of the cipher disk, the aluminum cylinder was constructed of 25 individual disks with the 26 letters of the alphabet set in the edge of each disk in random sequences.
The M-94 was six inches long and had a diameter of two inches. No two disks had the same sequence of letters. The disks could be fixed in any arrangement, with an external bar running the length of the cylinder to aid in aligning the disks and reading the resulting cipher.
The user arranged the disks to spell the first 25 letters of his message, then read the enciphered message off another row. The recipient set up the enciphered message on his device and then read the plain text message. The M-94 provided a fast and efficient method of enciphering and deciphering messages, although security was limited.
