Riverbank Publications No. 20 Several Machine-Ciphers and Methods for Their Solution 1st impression.
Riverbank, Geneva Ill. Riverbank Laboratories Department of Ciphers 1918. First Edition. [2], [1]-58, [28] pages 28.5 cm. Provided in the originally issued Riverbank Laboratories button and string flapped manila envelope with limitation number on outside (tear at flap fold). Individually numbered limitation of 200 copies (so stated on copyright page)..... More
