Mullard VP13C thermionic valve, 1934-1988
1934-1988
1934-1988
1939
1929-1972
1920-1936
circa 1970
1965
1931
1960-1964
1959
1950-1970
circa 1956
1960-1964
1965
1946
1948
1955-1980
1930
1965
1948
1940
1940
1948
1930
1927
circa 1940
1960
1965
1923
1948
1950-1970
1950-1969
circa 1935
1938
1940
1939