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细节
An early 19th Century 9in. radius vernier octant by McBride & Kerr
the ebony frame with brass fittings and inlaid ivory scale divided
5- 0- 100, vernier with fine screw adjustment, signed on the
cross bar McBride & Kerr with turned ivory topped pencil, double pin-hole sight with swivel shade, three shades and two mirrors, the
back with inlaid note plate and pin feet (two replaced, varnished
overall), together with keystone box (later) with trade label for Duren & Costigan, New York, length -- 13in. (33cm.)
See illustration
the ebony frame with brass fittings and inlaid ivory scale divided
5- 0- 100, vernier with fine screw adjustment, signed on the
cross bar M
back with inlaid note plate and pin feet (two replaced, varnished
overall), together with keystone box (later) with trade label for Duren & Costigan, New York, length -- 13in. (33cm.)
See illustration