The American VT-119 is an EHT rectifier. We have the commercial 2X2 and the variant 2X2A in the museum.
The 2.5 volt was the American standard voltage for early AC heated valves before the 6.3 Volt heater became standard in the mid 1930's.
The envelope has etched identification for the commercial Types 2X2 and 879 showing direct equivalence.
Within the anode bell can be seen the coated cathode tube. This has a small diameter in relation to the bell as the emission required is low but the gap needs to be large to avoid breakdown when a high Voltage is applied.
The cathode coating is only sprayed on along the length of the anode. The strapping of the cathode to one side of the heater can easily be seen. The heater spirals around an inner core. The cathode tube is closed at the top.
The classic envelope is 38 mm in diameter and, excluding the UX4 base pins, is 95 mm tall.
References: Datasheet, 3002 & 1043. Type VT-119 was first introduced in 1939.