The CV1306 is a double diode triode based on the HL23DD. The old service code is AR8.
The KB/V identifies this valve as being made to specification K1001 or K1006, the B denotes qualification by a UK authority and the V identifies the maker as Cossor, Highbury, pre Sept 1945.
The reverse is plain zinc loaded screening paint.
Looking into the top of the valve reveals little other than the two rectangular top micas.
The classic envelope is 32 mm in diameter, and excluding the MO base pins is 83 mm tall.
Reference: Data-sheet. Type CV1306 was first introduced in 1938. See also1938 adverts.
