
Double chambered vacuum tube with separating wall pierced in two places
1891
1891
1948-1950
1905
1879
1907
1938-1948
1705
1925
1855-1883
1906
1948-1960
1936
1898
1891
1891
1955-1965
1907
1891
1898
1879
1891
1891
1891
1876
1898
1891