Ritow Cylindrical Slide Rule
Frederick Post model 1475  [1925-1930]
 

This identical page appears in the 1925, 1927 and 1930 Frederick Post Catalogs
I know of no specimen of model 1475 and I doubt that any were ever actually made.  The September 1927 Post Price List says "Price on Request;"  The April 1930 Price List says "Discontinued." 

"Figure 31" is from "Elementary Slide Rule Manual" by H. Ritow, Published by the Frederick Post Co, Copyright 1925 where it is identified as a picture of the Ritow Cylindrical Slide Rule.  (There are no pictures of a Ritow Cylindrical Slide Rule in any Post catalog.)  It appears similar to Fuller's cylindrical slide rule.