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细节
An 18th-Century brass swinging-arm protractor,
signed on the base line Adams London, the arm with vernier scale and chart pointer, the scale divided 0°-180°-0°, the base line -- 10in. (25.4cm.) wide
See Illustration
signed on the base line Adams London, the arm with vernier scale and chart pointer, the scale divided 0°-180°-0°, the base line -- 10in. (25.4cm.) wide
See Illustration