DescriptionPolyphase (Mannheim type) 10" slide rule, 4053-3, made by Keuffel & Esser Co., New York, copyright 1900, made and issued circa 1915-1922. Mahogany, machined and laminated, with laminated white celluloid plastic ruled ("engine divided") scales in red and black; bottom edge has laminated scale (sine); 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 (cursor) not original; later replacement is a clear plastic (xylonite) model. Back has an inset printed table of settings, formulas and ratios. No serial number as typical in this era. Lot number blind-stamped on left end of rule and slide: 185. Lacking: original instruction booklet, box or case. Missing clear plastic (xylonite) window at right edge. Accompanied by brown leather case (sheath), probably not original. Scales are on the right: A, B, CI, C, D. With slide inverted: A, S [L], T, D. Engraved at center front with company name, "Keuffel & Esser Co., N.Y.", along with "Pat. June 5, 1900." This date is not relevant to the manufacture date. According to experts, this model was not issued before 1909. Without the original cursor and case, dating this item more precisely is difficult. Comparision to images of rules in the collections of Eric Marcotte and Clark McCoy suggests the 1915-1922 period. Notable is that the printed table on the back has variants. On the back of this one, at the lower right, the 'R' in "rad." and "radius'" are capitalized. Significance, if any, of this point in dating it is unknown. K&E had their main office and factories in Hoboken when this item was made.