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