Existing comment:
The Union / Federal Cipher Disk:
Union Chief Signal Officer General Albert J. Myer (AJM) used this cipher disk to send secret signals. The key would be determined prior to sending the message and would change frequently so it was less likely that signals would be intercepted and decrypted. Set the letter "R" on the inner disk to the "8" on the outer disk.
Try your hand at deciphering the message:
1188 1881 81 111 811 181 8181 |