Planimeter.
Fullsize image: https://s3-us-west-1.amazonaws.com/h...r_fullsize.jpg
More: https://en.wikipedia.org/wiki/Planimeter
Previously:
Custom bowling ball hand measurement tools - photo
Wet film thickness measuring tool - GIF
Spherical densiometer for measuring forest density - photo
O-ring measuring calipers - photo
Tool for measuring the flat on the end of a single point threading tool - video
Craniometer for measuring human skulls - photo
Tour de France sock height measuring tool - photo
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