A lovely example of a mid to late brass 17th Century Graphometer signed 'Bernier au niveau Paris'.
This is a surveying instrument used for angle measurements. It consists of a semicircular limb divided into 180 degrees. The limb is subtended by the diameter with two sights at its ends. In the middle of the diameter a "box and needle" (compass) is fixed. On the same middle the alidade with two other sights is fitted. The device is mounted on a staff via a ball and socket joint. In effect the device is a half-circumferentor.
This is without it's compass. It measures 19cm in length x 9 cm high x 9cm deep approx. It is fitted in a later box.