The CV1947 is a UK Government procurement specification for the commercial 6L6G. The valve is is a larger more powerful audio beam tetrode than the 6V6 receiver type. This was used for audio amplifiers and modulators for small Amplitude Modulated transmitters.
The ribbed and blackened anode with side flanges for both fixing and additional radiating area.
The cathode is a flattened tube and the control grid extends beyond the anode to the lower mica. The screen grid is not seen but the bright beam plates are visible on either side.
The top mica showing the cooling collar around the tops of the control grid supports.
The classic envelope is 50 mm in diameter and, excluding the IO base pins, is 116 mm tall.