This exhibit was at one time a fairly common EHT rectifier for military and professional applications.
The peak inverse voltage is 40 kV and the peak current is 150 mA. Typical output (around 250 W) would suit the requirements of a small airborne radar transmitter.
The Type designation on the base cap.
RCA and Made in USA.
The anode bell suspended from the top and the coiled filament is mounted between the two supports that can be seen. The distortion of the glass prevents imaging the filament.
The classic envelope is 51 mm in diameter and, excluding the UX4 base pins, is 139 mm tall.