The VU134 is a half wave EHT rectifier. It would have been designed for provision of EHT in such applications as Cathode Ray Tube indicating instruments. Radar and Oscilloscopes primarily.
The cylindrical anode is mounted on glass rods and connects to the top cap.
The cathode has dual supports fixed to the pinch as all the support has to come from the rods within the anode.
The white tube is the oxide coated cathode. The separation of the cathode from the anode indicates its high voltage design.
The top mica holding the cathode tube is held firmly by the two support rods.
The classic envelope is 43 mm in diameter, and excluding the B4 base pins, is 109 mm tall.
References: Data-sheet, 1040 & 1043. Type VU134 was first introduced in 1937. See also1937 adverts.