This exhibit is marked 2K25 in paint on a CV2792 valve. The B variant denotes the specific frequency range as the screw adjustment, seen on the right, has a range of a few tens of MHz only at 3 cm wavelengths. These reflex klystrons were used for the x-band (9.xx GHz) radar as well as in industry.
This valve and its waveguide mount are part of the Microwave Museum and belongs to Chris G0FDX.
This image shows the square waveguide 16 flange that connects this source to the rest of the waveguide system. The rings gut into the face of the flange form an RF choke.
The valve is held in place in the modified IO valve-base by the threaded locking ring.
The two spring plates on the right are separated by the screw mechanism and this movement adjusts the internal geometry slightly. The top of the valve has grooves in it to allow for this small displacement.
