The CV2487 is the commercial 4X250B and this example was made in the UK by STC. The 4X250B seems to be interchangeable with the 4CX250B. The base ring is connected at the base to pin one. This was for better performance at the higher frequencies.
The design is described as a radial beam power tetrode. Typically the cage grids are arranged so that the wires are optically aligned. SeeQV1-150A for details.
The valve would be operated in the special base and fitted with a ceramic chimney. Air would be forced from below through the chimney to cool the valve.
This is a new valve and is still sealed in polythene. The silver plating thus shows no sign of tarnishing.
The anode in the centre is surrounded by the folded metal tape that provides great surface area for the cooling air to pass over.
The label on the box shows that it was supplied to the Air Ministry on January 21, 1971.
The Inner packaging of the box is this shaped foam insert with foam plugs top and bottom.
The thin metal tube envelope is 34 mm in diameter, and excluding the B8F base pins is 47 mm tall.