Mullard EF9 VM RF pentode valve (McVitie Weston valve collection), 1939
1939
1939
1920-1936
1929-1972
1934-1988
circa 1970
1950-1970
1950-1970
1940
1939
1940
1933
1931
1929
1939
1935
1931
1929
1927
1940
1935
1935
1931
circa 1925
1939
1940
1937
1929
1931
1948