A late 18th Century ebony octant with bone scale and makers plaque stamped 'Made for Bartholomew Downing Oct 21, 1794', with pin hole sight, three shades, back sight and mirrors, the index arm -- 13 5/8in. (34.5cm.) radius, engraved 'Owens, Liverpool', bone vernier and clamp, with trade label, for 'Richard Patten, Instrument Maker, 180 Water Street, New York' inscribed 'All instruments in the above line made to order & warranted being divided on an Engine after the Plan of Ramsdens', in stepped keystone case