Jacob Amsler (*1823-†1912), Schaffhausen.

This electrum planimeter is an older version of model 1 and differs from the one illustrated in Amsler's 1930s catalogue. Serial number 41661 dating from ca. 1910.  

Very early unsigned Amsler type 4 brass planimeter with serial number 4107, c. 1866.

The paper label on the case with the inscription 'Planimetro' along with a calibration date (?) indicates that this planimeter was still in use in 1931 in Italy.  

The Musée des Arts et Métiers

in Paris have 2 early model 4's; one no. 3691 dated c. 1865 and another no. 5361 dated c. 1868.

Type 5 pantograph-planimeter made by or for Kern Aarau. Made of electrum, serial number 36221, ca. 1900.

Standard size type 6 planimeter is similar to type 4 but with steel points on top of the tracer arm for rapidly finding the mean height of indicator diagrams. Made of electrum, serial number 26247, dating from ca. 1900.

Type 6 was produced in 3 sizes.

Exceptionally long planimeter (47cm) with steel points on top of the tracer arm for rapidly finding the mean height of indicator diagrams. This instrument is the largest variant of type 6. It is lacking the knob on the tracer arm. Serial number 77969, ca. 1935.