Description and Notes:
Planimeter is an instrument for measuring the area of any simple closed curves, constructed based on the principle of the Green's theorem. The first morden planimeter was devised by the Swiss mathematician Jakob Amsler-Laffon in 1854. The one showing here is a sliding-arm polar planimeter, which is the type 6 of the original Amsler planimeters. The special feature of which is that it has two steel points on top of the tracing arm for rapidly finding the mean height of Indicator diargrams and of other diagrams.
It has been noted on the title page of the Amsler planimeters manual from the 1930's, "Over 83,000 Amsler Original Planimeters are in use in all parts of the World....The quality, reliability and accuracy of adjustment of each instrument is guaranteed by the facisile signature of the inventor J. Amsler, which is engraved on every real Amsler Orignial planimeter." As this planimeter has a serial number of 66839, therefore it can be dated to 1930 or earlier.