Moving magnet galvanometer with upright graduated metal disc
1875-1949
1875-1949
1877-1904
1837-1899
1901-1970
1906
1970
1910-1940
1872
1900
1962
1880
1913
1920-1926
1882-1900
1900
1901-1913
1880
1864-1887
1913
1927
1900
1940
1943
1918
1967
1882-1900
1912
1930
1900-1919
1900
1919
1870-1873
1930-1935
1904
1965-1980
1901-1970