VT 98A air-cooled power triode, used in radar transmitters, 1939-45 VT 98A air-cooled power triode 1939-1945
water cooled triode, with copper fillament. In wooden case with mesh windows. manufacturer unknown Water Cooled Triode
G.E.C. type CAT30 Water Cooled Triode, with directly heated Thoriated Tungsten Filament G.E.C. type CAT30 Water Cooled Triode 1955-1970