The CV1884 is the UK Government procurement specification for the commercial 33A/158M. The CV1884 is a 12 Watt anode dissipation transmitting double triode. The required drive is 1 Watt and the output is 15.5 Watts at up to 100 MHz.
The blackened anode with the grid visible above the lower mica and grid cooling fin above the top mica.
A closer view of the lower components. On positive signal peaks the grid can pass 12 mA.
The wide glass tube envelope is 28 mm in diameter, and excluding the B8B base pins is 63 mm tall.