This famous cipher was used for message encryption by the Union Army during the American Civil War (1861-1865). It was primarily a system used for flag signals where there was a line of sight, or for encrypted morse code messages.

The letters A.J.M. on the disk are for the inventor and Chief Signal Officer of the Union Army, Albert J Myer. His system was called Flag Telegraphy or "Wigwag".

Each disk has a unique serial number as was used in the original wheels.  Featuring National Archives branding on the back, the packaging includes instructions.