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