
McVitie Weston valve collection, Marconi WT Co., round valve, type N
circa 1913
circa 1913
1919
circa 1914
1917
1916
circa 1919
1919
1916
1935
circa 1925
1912
1931
circa 1913
1932
1919
1935
1932
1903-1907
1912
1960
1900-1920
1931
circa 1940
1923
circa 1935
1922-1923
1955