M-94

From the Wikipedia page with links to more technical descriptions.
The M-94 was a piece of cryptographic equipment used by the United States army, consisting of several lettered discs arranged as a cylinder. It was also employed by the US Navy, under the name CSP 488.
The device was conceived by Colonel Parker Hitt and then developed by Major Joseph Mauborgne in 1917; based on a system invented by Thomas Jefferson and Etienne Bazeries. Officially adopted in 1922, it remained in use until 1945, when it was replaced by more complex and secure electromechanical rotor machines, particularly the M-209.
Category:Encryption devices