Mullard VP13C thermionic valve, 1934-1988
1934-1988
1934-1988
1939
1929-1972
1920-1936
circa 1970
1965
1960-1964
1931
1959
1950-1970
1960-1964
1965
1946
circa 1956
1955-1980
1948
1930
1965
1948
1940
1927
1948
circa 1940
1965
1950-1970
1940
1948
1930
1950-1969
1960
1938
1923
1940
1933
1940