Image:Civil War cipher disk.jpg

Photographs scanned from public domain book:

• Brown, J. Willard, The Signal Corps, U.S.A. in the War of the Rebellion, U.S. Veteran Signal Corps Association, 1896, (reprinted by Arno Press, 1974), {{ISBN|0-405-06036-X}}.

{{PD-US}}

{{Copy to Wikimedia Commons|bot=Svenbot|priority=true}}