Mullard VP13C thermionic valve, 1934-1988
1934-1988
1934-1988
1939
1929-1972
1939
1920-1936
circa 1970
1931
1960-1964
1959
1946
1960-1964
1950-1970
circa 1956
1955-1980
1930
1948
1948
1940
1927
circa 1940
1950-1970
1950-1969
1940
1948
1960
1938
1923
1930
1933
1940
1926
circa 1929
1966