This is an antique 18th century brass French sector. A sector, also referred to as a proportional compass or military compass, is a tool used for mathematical calculations. The inscription actually reads Pre le Maire Paris, which means it was made for the First (premiere) Mayor of Paris. The first mayor of Paris was Jean Sylvain Bailly who was elected during the first French Revolution in 1789. He was in office from 1789 - 1791 and is presumably the original owner of this brass sector. Poids de Boulets translates to 'weight of balls' making the use of this sector instrument to be like gunner's calipers which measured the outer diameter and the interior bore of a cannon ball to determine the angle and shot of the ball from the cannon. The estimate is based on actual past recorded auction sales of comparables and factors in the provenance of likely original ownership.