This identical page appears in the 1925, 1927 and 1930 Post catalogs.
The "Sectional View Showing Construction" is reprinted from the 1910 Post catalog; it also appears in D&P catalogs from 1906 to 1919.   It shows Dennert and Pape's DRGM 192052 friction adjusting mechanism.   However, All Post brand slide rules (including "Ritow" rules) from 1925 to 1930 were made by Koch, Huxhold & Hanneman, not D&P. 

For more information about Herman Ritow and Post "Ritow" slide rules, click here.