A plastic 4-pin base with tipless domed envelope. Stamped on envelope: "83". Donor’s card reads: “Full-wave mercury vapor rectifier made by the Radio Corporation of America about 1935 or before.
A 4-pin plastic base with top contact, ceramic insulator, S-shaped envelope. Donor’s card reads: “Half-wave mercury rectifier made by the Western Electric Company about 1935. Filament: 2.5 volts at ...