AF triode valve (McVitie Weston valve collection), 1906-1972
1906-1972
1906-1972
1935
1920-1933
1936
1889-1900
1955
1900-1920
1930-1950
1920-1940
1914-1945
1907
1905
1900
1920-1940
1922-1929
1900-1920
1906-1908
circa 1934
1955
1913-1914
1933
1932
1933
1940-1970
1958
1979
1911
1940
1935-1955
1900-1919
1931
before 1889