The CV2246 is a Geiger Muller radiation detection tube. It was used in the UK Contamination meter number one.
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 two pins in the rubber outer sleeve.
British Military Meter, Contamination, No. 1. Image courtesy Lampes and Tubes
The wide rubber outer tube envelope is 25 mm in diameter, and excluding the base pins is 110 mm tall.
