Ships Navigators Quadrant From 18th Century

Antique T frame quadrant with engraved bone makers plate from Gilbert of London. With scale that reads to ninety degrees. (Scale shows repairs). There are two sun filters and two horizon sight filters. Also fitted with two peep sights. The maker John Gilbert was active on Tower Hill, London between 1723-1767. Brasses show heavy patina. 18"Hx15"Wx3"Dia 5lbs.