The M-94 was a W.W.II United States Army Signal Corps cipher device used from the early 1920's up till 1942 as a low level, tactical, cryptographic encoding/decoding device. A version used by the U.S. Navy was called CSP-488. It was also called a Jefferson device and was similar in type (if not identical) to Major Bazeries Cipher Device or Bazeries Cylinder. Over time, these units were replaced by the M-209 cipher machine.

A view of the M-94 showing wheel markings. (Courtesy marvinh@midwest.net)