The CV133 triode was specified as both an amplifier and an RF power valve and in commercial form is a 6C4, the valve the specification was based upon.
As an RF amplifier (Class C) it would deliver 5.5 Watts.
With the very small envelope volume, this would make it ideal for hand portable equipment. In larger apparatus it could deliver enough drive power for much larger PA's.
The KB/ZA identifies this valve as being made to specification K1001 or K1006, the B denotes qualification by a UK authority and the Z identifies the maker as MO Valve Company, Gateshead, pre March 1957.
The pressed anode is stitched together, ribbed for dimensional stability and blackened to improve heat radiation. The control grid can be seen where the anode is notched.
Side view.
The thin glass tube envelope is 18 mm in diameter, and excluding the B7G base pins is 46 mm tall.
