DescriptionSlide rule, model 4055 (advanced Mannheim type), 10 inch, made by Keuffel & Esser Co. in Hoboken, no date, circa 1937-1943. Mahogany with white celluloid, engine engraved; chart on back printed with clear covering; "frameless" (thin aluminum frame) glass cursor with white celluloid slides (broken with missing sections on this part.) Serial number: 939481. Front scales: A [B C] D. Back is labeled S, L , T. Front has has company name and the patent number 1,934,232 which was granted in 1933 to Adolf Keuffel for advances in adjustments of this slide rule type (it is related to the three screws on the back.) The cursor which has just enough of the slide left to indicate the last two numerals of a patent number that was on the bottom edge, "02"; this was patent number 2,086,502 granted in 1937 for an advanced cursor (see objects 2008.012.0123 for a model no. 4054 with the same cursor having this patent number.) This model number does not appear in company catalogs after 1943. With the high serial number and the end of production in the 1940's this slide rule is likely to be from the later end of the 1937-1943 date period. Although marked "N.Y." the company did its manufacturing in Hoboken at this time.