The CV808 is an RF double triode for battery operation and at up to 40 MHz. The data sheet for the commercial DCC90 says the design purpose was as a push-pull RF amplifier or oscillator and the rating are for intermittent operation. With two Watts of RF output in the HF section of the spectrum, a short range portable radio is indicated. This suggests professional/military voice communications.
The KB/D identifies this valve as being made to specification K1001 or K1006, the B denotes qualification by a UK authority and the D identifies the maker as Mullard Radio Valve Co., Mitcham.
The face view of one anode. A low power valve so the nickel sheet is left bright.
The twin box anode triode sections.
The thin glass tube envelope is 18 mm in diameter and, excluding the B7G base pins, is 47 mm tall.