M-94 Cipher Device

The M-94 was widely used from 1922 to 1943 by the U.S. Army as tactical, cryptographic encoding/decoding device. Using the same principle as Thomas Jefferson’s cipher device, disks are rotated to encipher a message. During World War II, the M-94 was replaced by the more complex M-209 (1943). Nearly 9,432 of the M-94s were made between their adoption in 1921 and their replacement by the M-209.