BRASS BOX SEXTANT fully signed below the silver scale "W. & S. Jones Holburn London". 3" diameter. Horizon glass with sun shade that slides into place by using a small lever that's recessed into the side of the brass drum. 2" long index arm fitted with with a sophisticated fine adjusting device. Swing away magnifier. Removable, two draw, optic that can be used in place of a peep site that slides into position by using a lever on the side of the brass drum. Bottom with a sliding door to allow in more light. Threaded removable cover with an engraved scale on the top. Condition overall fine with brass retaining a good deal of its original lacquer finish. William and Samuel Jones began a partnership in 1791 that lasted until 1859 when William died. Their instruments are always highly regarded for their superb quality. Circa 1845.