The CV1949 is a miniature thyratron. The prototype was the 6D4.
The KB/QG 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 - factory not known.
The box anode prevents seeing within.
The 6633 is not a secondary Type designation.
The thin glass tube envelope is 17 mm in diameter and, excluding the B7G base pins, is 45 mm tall.
