DescriptionDemonstration Slide Rule, Mannheim type, model 100, for 4053-3 Polyphase slide rule, made by Keuffel & Esser Co., (New York), no date, circa 1954-1962. Pine wood, machined and painted: off-white with lettering and scales silkscreened in red and black; top and bottom edges and back of stator painted white; left and right edges are unpainted. Overall: 85-1/2" wide x 7-1/2" high x 1-1/2" deep. Indicator: white painted machined wood with clear acrylic sheet, metal spring, 8-1/2" high x 6" wide. Invertable slide with scales as noted below; two single finger holes (3/4" diameter blind, unpainted), each varies from 27-29" from the end, on each side of the slide for faciltating the shifting of the slide. Model number does not appear on item. 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.) For classroom use in teaching use of the slide rule. It was intended to be mounted over a blackboard, probably permanently or semi-permanently. While the slide can be removed and inverted, the entire piece was not meant to be reversed, so there are no conversion scales on the back as were found on the actual slide rule. The 42nd edition catalog of 1954 stated that this was for the Polyphase [4053-3] and the Beginners' No. N4058W (which is not marked on this object.) In 1954 the company had dropped the 'N' for the 4053-3 and renumbered it again 1962, so it believed that this rule was made between 1954 and about 1962. K&E had their main office and factories in Hoboken when this item was made.