This rectifier has lost all of its markings. From the pattern of the base pins and the fact that it is a rectifier, makes the identification much easier. The choise is an R13A from Ferranti or an EZ35 or 6X5 or U147.
It is a standard full wave HT rectifier for low power AC mains driven equipment. The output of a centre tapped transformer would be applied to the anodes, the rating given is 325-0-325, the common cathode would be the output for the rectified voltage. A effective series resistance of 350 Ohms was required to limit surges and the reservoir capacitor had to be restricted to 16 µF. The valve has two anodes stacked vertically on a common cathode tube.
With the pinch on the left the picture shows the twisted heater entering the cathode tube. The cathode passes through the first anode and through a separating mica to the top anode. Each anode has a support fin and two outer circular sections. These outer cylinders continue with the carbonising and are there to provide a greater surface area for heat to be radiated away from the anode.
Here the arrangement of anode connections can be seen. The main supports pass through the length of both anodes and to the mica supports. The anode fins are attached to one support each.
Mica supports and the anode clamped to the foreground support rod.
Looking into the anode it can be seen that the cylindrical radiators do not close round the cathode but leave a small gap. Through this gap we can see the common cathode tube.
The classic envelope is 39 mm in diameter and excluding the IO base pins the valve is 91 mm tall.