French Brass Sector Compass Or Proportional Compass, 18th Century.

A two hinged arms with engraved scales — classic sector design.
Engravings like “Guides”, “Polygones”, and degree markings are mathematical/engineering scales.

The decorative pivot at the joint is typical of 18th century mathematical instruments. Made of brass, with hand-engraved numbers and script, not machine-etched. Made in Franch,

A sector was a calculation tool, used before calculators existed. Depending on the scales, it could be used for:

Geometry and trigonometry
Constructing polygons
Proportional scaling (maps, drawings, architecture)
Military and artillery calculations
Surveying and navigation
Engineers, architects, surveyors, and military officers commonly carried these.

In a used but very good state.

Dimensions:
long: 16,5 cm
wide: 2,9 cm

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