The limb is subtended by the diameter with two sights at it's ends. It also has an alidade in the middle where two other sights are fitted. The device is mounted via a ball and socket joint. In effect the device is a half-circumferentor. This rare item is solid brass, and has been polished and laquered to a high standard.Made by the world renowned scientific instrument manufacturers, Stanley of London. It is presented in a fitted woodenbox. The item "EARLY BRASS GRAPHOMETER by STANLEY of LONDON FITTED WOODEN BOX" is in sale since Sunday, July 15, 2018. This item is in the category "Antiques\Science/Medicine\Scientific Instruments". The seller is "barnowl582" and is located in Orpington. This item can be shipped worldwide.