Rare early vernier sliding gauge, circa 1850.
Nickel silver (German silver) and steel, measuring up to 4 inches, the frame engraved ROSS, London. Similar to the pattern shown, courtesy of Charles Frodsham, in Britten's Watch and Clockmakers' Handbook..., under 'slide gauge.' See also Crom, page 476. Total length when closed 7 inches (17.5 cm).
Andrew Ross, mathematical instrument maker, working in London (mostly Clerkenwell) from 1830 to 1860. See Clifton Directory of British Scientific Instrument Makers 1550-1851.
In fine original condition.
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