The CV1949 is a miniature thyratron. The prototype was the 6D4 - also on the glass of this exhibit.
The KB/Q identifies this valve as being made to specification K1001 or K1006, the B denotes qualification by a UK authority and the QG identifies the maker as English Electric Valve Co., Chelmsford.
There is heat sinking on the control electrode top and bottom.
Another view but little is revealed.
The thin glass tube envelope is 17 mm in diameter and, excluding the B7G base pins, is 47 mm tall.
