The valve is rated at 450 W output power, and is radiation cooled. The filament is a single thread formed into an inverted 'V', and sprung loaded at the top.
The grid is a wire helix and it can be seen extending beyond the enclosing anode cylinder with a mesh end. The anode is not substantial or blackened to assist radiating away the heat generated by the electron bombardment.
A side view of the grid end mesh.
The grid helix proper.
A close-up view of one end cap showing connecting wires.
The other end.
The anchor motif.
The balloon envelope is 150 mm in diameter and, excluding the base pins, is 330 mm tall.
Reference: Datasheet. Type NT19 was first introduced in 1933.