Proportional compass

This proportional compass is a measuring device used to solve trigonometry problems and square root calculations, and for studies in geometry and proportion using Euclid's theory of similar triangles.

It consists of 2 rulers, usually made of copper, which are the same length and joined by a hinge allowing them to be used as a compass. Straight lines with various measurements emerge from the axis and are identical on both sides.

The caliper was invented during the Renaissance when a simple instrument was required for doing arithmetic and geometric calculations. It was used for topography and navigation among other disciplines.

This compass bears the inscription "Metz Amsterdam" on the back. Coenraad Metz was an artisan scientific instrument maker who was born in Danzig but settled in Amsterdam from 1660. He founded the Metz company, which was run by his grandson during the 18th century. It became one of the main providers of telescopes to the Dutch East India Company (VOC).