Keuffel & Esser 4181   Log-Log Duplex Decitrig

The K&E 4181 family was manufactured in the United States from 1953 to 1962. These model evolved from the 4080 and 4081 families, but the 4041 were fabricated with Ivorite, (Acrylonitrile Butadiene Styrene (ABS) CYCOLAC™ Resin ), a smooth, white, and long wearing plastic. Scales were printed on the Ivorite, and the indicator was made with glasses hold on plastic ends with screwed metallic frames. 

This model was fabricated in three different sizes: 4181-1 (6 in - pocket), 4181-3 (12 in - handheld), and 4181-5 (22 in - desktop). In 1960-1962 the K&E renamed the 4181 family; 4181-1 became 68-1287, 4181-3 became 68-1256 and the 4181-5 became 69-1200. These new versions were known as the Jet-Log-Log Decitrig family.  

The scales on this model were; on the front side: LL01, L, K, A [ B, T Cot, SRT, S Cos ] D, DI, LL1, and in the back side: LL02, LL03, DF [ CF, CIF, CI, C ] D, LL3, LL2, where the scales in parenthesis are on the slider.

 The original costs of the 4181 family rules shown in the 1953 price catalog is: the 4181-1 cost is $9.25 ($104.22 in 2023 USD), while the 4181-3 is priced $15..00 ($169 in 2023 USD).

References:

• 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