A rare hydrographic surveying sextant also known as a "Quintant" because of the increased size of its scale, reading to 165 degrees. In this lovely example, signed "Cary, London," the scales are engraved on gold and platinum and it bears British Admiralty Hydrographic Survey markings. Such instruments were used to take triangulation sightings when making soundings for Admiralty charts. Note the addition of a bubble level on the index arm just above the vernier magnifier. Not visible in this photo is the unique system of sextant frame stiffening that the Cary firm incorporated into this design. Circa 1850. (Collection West Sea Co.)