DescriptionSlide rule, model 4041 (Mannheim type), 10 inch, made by Keuffel & Esser Co.in Hoboken, no date, circa 1900-1915. Mahogany with white celluloid, engine engraved; chart on back printed with clear covering; aluminum framed glass cursor. Lot number 779 as blind stamped on left end. With dark reddish brown moroccan leather covered slipcase with gilt stamping: Keuffel & Esser Co. Mannheim Slide Rule. Slip end is in pieces. Main case has damaged end with loss and tape repair. Note the front scales are not labeled: front would be A [B C] D. Back is labeled S and T with the [L] scale not labeled. Bottom edge is centimeter rule, top edge is English rule measurements. The dating of this item is only approximate. On body under slide is engraved: Pat. June 5, 1900. The lot number is not a firm method of dating this item at the present except that it is definitely in this time period. According to collectors' sources, this cursor style, framed with aluminum, evolved into one with thinner metal around the glass up to 1915 when the so-called "frameless" cursor was the new style. Although marked "N.Y." the company did its manufacturing in Hoboken at this time.