General area measurement and finding the mean height of indicator diagrams
Notes: "This planimeter has two upward pointing spikes, one at the end of the tracing arm and the other on the frame. These serve the same purpose as the similar spikes on Amsler Type 6 planimeters: measuring the mean height of steam engine indicator diagrams. Also, something rarely seen: two weights, one for the pole arm and one for the tracing arm. The serial number, 4434, indicates that this planimeter was made in 1913."
