Keuffel & Esser Log-Log Duplex Vector 4093-3

The Log-Log Duplex Vector 4093-3 was produced in the United States from 1930 to 1938. It was fabricated from mahogany wood covered with white celluloid were scales were engraved. The cursor for models before 1936 was initially all glass screwed to plastic ends, and for later models the regular metal rimmed glass cursor with plastic ends. The rule was hold with metallic braces. This model, patented in 1924, is the first of the K&E Log-Log Vector Rules, and was designed by an expert Electrical Engineer: Mendell Penco Weinbach. This model was the first to include the Hyperbolic Scales: Sinh and Tanh, and to use the decimal division of the trigonometric scales.  This model was very useful for Engineers and Scientists, but specially for Electrical Engineers (1). 

The scales on this rule are:  L LL0 DF [CF B CI C] D LL2 LL3 on the front face, and Sh1 Sh2 Th [SI1 SI2 TI] D S T on the back face. K&E catalogs show that this model was produced in two sizes: 4093-3 (12 inches) and 4093-5 (22 inches). According with the serial number on the item in this collection, and the information in Clark McCoy's website, this rule was manufactured  in the period 1932-1933, and had a price of $12.85 ($297.37 in 2023 USD)

References:

(1). McCoy, Clark: K&E 1933 Catalog, Log-Log Vector Slide Rules. http://www.mccoys-kecatalogs.com/KECatalogs/1933/1933KEp14.htm 

• McCoy, Clark: Keuffel and Esser Catalog Site. K&E Catalogs and Price Lists for Slide Rules.  http://www.mccoys-kecatalogs.com/KEmain.htm 

This website is the most extensive digitla file of Keuffel and Esser product catalogs and price lists (prices  shown here were taken from these lists)  from 1881 until 1972. You can find also user manuals for many slide rule models, as well as other interesting brochures and materials.

• Shawlee, Walter: Keuffel & Esser Co. Slide Rules. https://www.sphere.bc.ca/test/ke-sliderule.html 

This website gives a good overview of models, and other interesting information and links