A late 18th-Century ebony framed octant signed on the makers ivory plaque Spencer, Browning & Rust London and inscribed with the initials W.W.K., with double 'pin-hole' sight and slide, back sight, mirrors, three shades, the brass index arm with brass framed ivory vernier scale and clamp, the arc with engraved ivory scale divided 0°o-100°o resting on three pad feet, in stepped mahogany case with trade label for Samuel Thaxter No. 125 State St. Boston - 14½in. (37cm.) wide.