Keuffel & Esser 1102 Amsler Style Polar Planimeter

This German silver instrument has two arms pivoted at one end. One arm has a tracer point and index marks for four ratios: 1 square D. (centimeters or meters, perhaps), 15 square inches, 10 square inches, and 10 square K. (probably chains). A screw assembly adjusts the length of the tracer arm. A support for the tracer point prevents it from tearing the paper. Two numbers are stamped underneath the arm: 35, which is also underneath the tracer point, and 381.

The other arm is jointed. A notch in the jointed part of that arm fits around a screw that in turn fits into a rectangular metal weight that is faced with brass. The weight is marked: 381. A piece of paper is attached to the bottom of the weight. A cylindrical German silver weight may be placed in the end of the arm. The longer part of the arm is marked: KEUFFEL & ESSER Co NEW YORK. It is also marked: 35. A carriage at the pivot holds a measuring wheel with vernier and a horizontal registering dial. A hardwood case has green velvet lining the supports. On the bottom of the case is written: BUREAU C AND R.

According to the accession file, this instrument was received at the Smithsonian in 1980.

Keuffel & Esser sold this planimeter as model 1102 from 1892 to 1901, and as model 4220 from 1901 to 1936. Since the rectangular brass weight was only depicted in catalogs before 1901, this example is probably a model 1102. However, the construction of the jointed arm is different from the illustration in the 1892 and 1895 catalogs. The jointed arm is like the illustration in catalogs printed between 1901 and 1936, but the brass weight is neither mentioned nor shown in these catalogs. The serial number, 381, dates this instrument as older than 1985.0112.218, whose jointed arm does not look like either of the catalog illustrations. That instrument has a celluloid measuring wheel, but that piece is made of German silver on this instrument.

References: Catalogue of Keuffel & Esser, 23rd ed. (New York, 1892), 104; Catalogue of Keuffel & Esser, 26th ed. (New York, 1895), 145; Clark McCoy, "Collection of Pages from K&E Catalogs for the 4220 Family of Polar Planimeters," http://www.mccoys-kecatalogs.com/PlanimeterModels/ke4220family.htm.

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