Frederick Post models 1435-37  [1910]

Post 1436 [1910]
(Courtesy Fred Astren).

The "Eureka" slide rules (models 1435 and 1436) are peculiar.  Although the catalog shows no scale labels, Fred Astren's specimen's scales are labeled A [B, A*] B on the left and A [B*, A] B on the right end.  The A-A scale runs from 1 to 3.16; the B-B* scale runs from 10 to 3.16 (inverted); the A*-A scale runs from 3.16 to 1 (inverted); and the B-B scale runs from 3.16 to 10.   There are three scales on the back of the slide:  [Ka, Q, Kb]  where Ka and Kb constitute a single scale for cube roots and Q is for quadratic roots.  It's not obvious how these rules could be used for multiplication or division. 

Models 1435 and 1436 appear to be the same as Dennert & Pape models 10 and 11 in the 1914-19 D&P Catalogs but the D&P illustration has the slide reversed. 

Model 1437, "Nautical," appears to be same as Dennert & Pape model 27 (1914 D&P Catalog only) 

"Adjustable" means the rule uses the D&P DRGM 192052 friction adjusting mechanism.