Riverbank, Geneva Ill. Riverbank Laboratories Department of Ciphers 1918. First Edition. 14, [2-blank] pages. 28.5 cm. Provided in the originally issued Riverbank Laboratories button and string flapped manila envelope with limitation number on outside (sunned on one edge, crease). Individually numbered limitation of 200 copies (so stated on copyright page). Stiff tan publisher's wraps with cover titles duplicating title page. Wrappers stapled (minor rusting), several offset stains from the flap ties and one additional stain (from old paper, now removed). Near Fine. Wraps. 
A restricted publication not publically available when issued, it appears in institutional collections, but is rarely found on the market.. '...written in collaboration with Mrs. Friedman, [it] took up where No 15 left off. It extended the method of that brochure to secondary alphabets that resulted from the interaction of two different mixed alphabets that had been used as the plain an cipher components.' (Kahn) Authorship attribution from Galland (with Elizebeth's name mis-spellled as Elizabeth]. [ Methods and examples of Deciphering]
See J.S. Galland, An Historical and Analytical Bibliography of Cryptology, page 68. See also Kahn, The CodeBreakers, 1996, p376, Shulman, An Annotated Bibliography of Cryptography, 1976, p82.