Dietzgen Phillips 1740, 1759B, & 1752P

The Dietzgen Phillips rules were manufactured in the United States from 1914 until the late 1930's. Fabricated with wood (mahogany?) covered with white ivorine (celluloid), machine engraved scales, and glass frame-less cursor. The distinctive characteristic in these rules is the Phillips Scale, a reverse double logarithmic scale (100-10-1) that is only the reverse of a standard A-scale. 

Models 1740 and 1759B basically have the same scale set, having only the Cubic scale, labeled E in these rules, in a different location, models 1759 on the lower rule's edge, and models 1740 on the front top. The model 1759B, produced until the mid 1920's, has scales A [ B, R, C ] D || E on the front face, and S, L, T on the slider's back side. It has a 10 inches ruler integrates on the top edge. The model 1740 has the scales E, A [ B, R, C ] D on the front face, and also S, L, T on the slider's back. This model also has a 10 inches rules on the top edge, and a 25 cm ruler on the lower edge. Both models have at the back the a table with the rule settings to perform Unit conversions.

Dietzgen produced the Phillips 1759 model in three sizes: 1759A (8 inches), 1759B (10 inches), and 1759C (20 inches). The other model was also produced in three sizes: 1738 (8 inches), 1740 (10 inches), and 1742P (20 inches)

In this collection I have two 10 inches 1740 and 1759B models, and one 20 inches 1752P model, and because these rules have no serial number or any other mark indicating the fabrication date, I can only assume the 1740 model was fabricated in the lapse 1915-1925 (I found in the WEB only a copy of the 1921 Dietzgen Catalogue including the 1740), while the 1759 and 1752P models between 1926-1936 (I found copies only of the 1928 and 1931 Dietzgen Catalogs).