A 19th Century ebony and brass octant, the ivory maker's plaque engraved 'Made by I.J. Messer. London for G.B. Gerraio Lisbon', the frame with ivory scale, three shades, mirrors, the index arm with tangent screw and clamp -- 8¾in. (22.2cm.) radius, in shaped case with trade label for W.E. Jewitt & Co., 2 Canning Place, Liverpool

細節
A 19th Century ebony and brass octant, the ivory maker's plaque engraved 'Made by I.J. Messer. London for G.B. Gerraio Lisbon', the frame with ivory scale, three shades, mirrors, the index arm with tangent screw and clamp -- 8¾in. (22.2cm.) radius, in shaped case with trade label for W.E. Jewitt & Co., 2 Canning Place, Liverpool