The IW3 is a full wave rectifier from the early days of mains radios with the 4.0 Volt heater that was standard at the time. With a current rating of 120 mA at 350 Volts this would have powered a substantial piece of equipment.
The twin rectifier sections. The insulated heaters have additional heater/cathode insulation in that the cathode is lined with a ceramic tube.
The anodes are stiffened with horizontal ridges.
Anode face view.
The balloon envelope is 54 mm in diameter and, excluding the B4 base pins, is 108 mm tall.
References: Data-sheet, 1040 & 1043. Type IW3 was first introduced in 1933. See also1933 adverts.
