The original 52KU was the Cossor code for the GZ32 full wave rectifier. This rectifier is a medium power device for general purpose use. It probably would have been used in audio power amplifiers or modest radio transmitters or industrial equipment.
This Russian made exhibit is also labeled as GZ32 and CV593.
The maximum reservoir capacitor for the 52KU was 16 µF and the minimum series resistance to limit current was 75 Ohms. Not quite the same as the Mullard GZ32.
The valve was made in the USSR. With state owned production facilities no other identification was deemed necessary.
The heater is coiled and ceramic coated. It can be seen that the heater is wired in parallel between the two rectifier sections. The cathodes are also connected in parallel. There is no return heater connection.
The heater wire is connected to the cathode tube above the top mica. The tube is crushed onto the wire. The emerging heater wire can be seen on the left.
The general construction. Note the leads emerging from the pinch as stout fixed length wires. The jig assembled electrodes between the mica supports would have been spot welded to the supports before the whole construction was passed to be encapsulated in the envelope.
The wide glass tube envelope is 28 mm in diameter and, excluding the IO base pins, is 80 mm tall.
References: Datasheet, 1040 & 1043. Type 52KU was first introduced in 1949.