09-033. Swiss, dated on the label in the lid "18 Sept 1919," signed "G. Coradi," serial numbered 3935, and described in the 1909 Keuffel & Esser catalog as follows: "Precision Polar Disc Planimeter, German silver and brass, with aluminum paper-faced contact disc for the measuring wheel, latest construction, adjustable tracer arm 13 3/4 in. fully graduated to 1/2 millimeters, with micrometer screw for vernier readings to 1/20 millimeter. Heavy pole-weight, 5 3/4 in. diameter, with table of settings for inches and metric measure..." This unusual polar disk planimeter is in very good overall condition, in its original somewhat worn plush lined cloth covered case.
"In this instrument the motion of the measuring wheel is independent of the condition of the paper on which the measured figure is drawn, as the measuring wheel revolves by contact with the plane disc. Reliable computations can therefore be made on plans after they have been folded or rolled..."
