All-in-one galvonometer by Pifco Ltd
circa 1932
circa 1932
circa 1920
1955
1930
1920
1910
1896
1930
1901
1935
1904
1905
1890
1905
1940
1941
1910
1895
1920
1915
1900
1930
1940
1907
1905
1920
1955
1955
1945
1905
1945
1950
1925
1910
1910
1890
1883
1945
1920
1885
1930
1930
1941
1940
1920