The 19BG6G is described in the data-sheet as basically a 6L6G redesigned for use as a television line output valve. It is fitted with a 300mA heater for series heater chain use. The main change in the valve is better insulation to cope with the high peak anode voltages.
Turned through 90 degrees the two halves of the anode can be seen.
The control grid is wound on copper supports. The screen grid is aligned to the control grid and its supports are hidden by the beam plate.
The top mica components. The heater can be seen to pass through the cathode tube eight times.
The classic envelope is 51 mm in diameter, and excluding the IO base pins is 124 mm tall.
Reference: Datasheet. Type 19BG6G was first introduced in 1949.