The CV5242 is a low noise VHF triode for grounded cathode operation and the UK government specification is based on the commercial A2599.
The design is of the frame grid type with cathode one side and anode on the other. This planar construction and the multiple cathode connections place the assembly part way to disc seal construction but at considerably less cost.
See alsoE2599 which looks like the prototype of this design.
The GEC paper logo.
The tiny electrode assembly within the standard B9A envelope. The box anode is on the right. The bright central support hold the frame grid.
Looking directly at the anode with the frame grid beyond. The frame is substantial as the grid wire is wound at half breaking strain to ensure a flat lay to the wire. At full size the grid wire can be seen.
Photomicrograph of one corner of the frame grid showing the individual wires. Frame grids only have one layer of wire that looks to be welded to the frame.
The thin glass tube envelope is 20 mm in diameter, and excluding the B9A base pins is 48 mm tall.
Reference: Data-sheet. Type CV5242 was first introduced in 1962.