The CV591 (commercially the 6SJ7) is a high gain screened pentode and dates from the mid 1940s. It is a sharp cut-off type and is specified for RF or AF use.
The KB/T identifies this valve as being made to specification K1001 or K1006, the B denotes qualification by a UK authority and the T identifies the maker as British Tungsram, Tottenham.
The Government up arrow.
The rest of the steel can is protected from corrosion by the black paint.
The thin metal tube envelope is 25 mm in diameter and excluding the IO base pins, is 51 mm tall.
