DescriptionPolyphase (Mannheim type) 10" slide rule, N4053-3, made by Keuffel & Esser Co., (New York), no date, circa 1941-1942. Mahogany, machined and laminated; with laminated white celluloid plastic ruled ("engine divided") scales in red and black; bottom edge has laminated centimeter rule; top front edge beveled with laminated white celluloid ruler, English measure by inches and sixteenths; 10-5/8" overall length x 1-5/16" high x 3/8" thick. Indicator "improved glass"; see description below. Back has an inset printed table of settings, formulas and ratios. Serial number 897007 which appears on the left end of slide back and on the left end of centimeter rule on bottom. With: tan leather hard case (RM) with space for magnifier (top is blindstamped K &E Slide Rule); magnifier 4185B. Case lacks part of flap; previous owner's name stenciled on back. Scales on front are marked at the right: A, B, CI, C, D, K. With slide inverted: A, S, L, T, D, K (note S, L, T scales are marked on right end of slide.) Model number is onright end of slide front. Engraved on stator at top left is the company name, "Keuffel & Esser Co. N.Y."; patent number just right of center, "Pat. 1,934,232"; "Made in U.S.A." starting about 3" from the right edge. Indicator is improved metal frame type with "Patent 2,086,502" on top; bottom is notched with a center marked black line for reading the centimeter rule. It does not have the usual K&E mark on that end. Conversion table on back is U.S. Bureau of Standards "Circular No. 47." Removable magnifier is marked on one side with "K.&E. Co. N.Y.", but model number does not appear on item. K&E had their main office and factories in Hoboken when this item was made.