Keuffel & Esser Polyphase Mannheim & 4097D

The Ever-There 4097-D model was manufactured in the United States from 1937 to 1954, when it was replaced by the 4161-1. Fabricated with Xylonite, a type of plastic or celluloid that resembles amber, coral, or tortoise shell, this pocket model 5 in long had the improved wire framed glass cursor. The 4097-D had 13 scales: A DF [CF CI C] D K on the front side, [B S L T] on the back of the slider, and inches - centimetres on the back side. The origional price of this rule in 1937 was $3.00 ($63 in 2023 USD)

K& E produced an 11 inches long mahogany celluloid covered version of the 4097-D, but it is not referred in any catalog or price list, so it is not possible determine the exact production years. I found this rule accidentally in E-Bay. At a first glance looked like a 4053 but the folded scales DF-CF, the slider over-length, a special instructions set on the back side that I have never seen in other K&E rule, and no model number or ID on it, catch my attention. Only a serial number at the edge next to the cm-scale, that indicates the manufacturing year

I looked in different specialist's websites, but the only reference I found was in the Herman van Herwijnen's Catalog and the entries read: NAME: Keuffel & Esser Polyphase Mannheim Adjustable, no model number shown, marked only "K+E" , MATCH NR: 4548 (link to an image), and under DESCRIPTION: Generic slide rule of Engine divided celluloid laminated mahogany, slide is 1/4 inch overlength on the right. Not too much info...

Next are pictures of this rarity  with my 4097-D.

 I found (Dec-2020) another rarity of this kind, that has really captivated me. This rule, on his back face, has the logo of the College of Engineering of the University of Washington, and an advanced formula chart that includes values of important Math constants, Metric-Standard  and Energy  units conversion. Basic Kinematics Formulas, basic Analytic Geometry formulas, Trigonometric Identities, Derivatives and Integrals tables, and other basic Physics formulas like Kinetic Energy and Inertia Moments.

According with the serial number on this rule, it seems that this specimen was fabricated between 1942-1943. I don't know whether or not this was a special edition for the College of Engineering at the University of Washington. It has also a different logo than the above rule.

Here are pictures of these rarities compared side-to-side:

References:

• McCoy, Clark: McCoy' K&E Catalogs: Mystery K&E Mannheim Slide Rules : 

//www.mccoys-kecatalogs.com/KECollection/Mystery/kemysteryfamilyrules.htm?fbclid=IwAR3pwQJkEB1vRZxvuYwxoiaDyc9sRuitN_3Q4qRWPDX_grpPEFrY5jieLbk 

• 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