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Hilger wavelength spectroscope, with camera, London, England, 1919
1919
1919
1871-1900
1850-1924
1850-1924
1875-1885
1900-1980
1875
1920
1871-1900
1880
1967-1973
1960-1969
1908-1928
1984
1863
circa 1920
1900
1885-1895
1865-1875
1984
1984
1865-1875
1850-1924
1984
1919
1919
1850-1924
1984
1984
1984
1874