The triode is at the top and below the middle mica is the screening box containing the diode anode. The anode forms a cylinder around the single strand filament and is welded to the support that can be seen on the right of the image.
The wide glass tube envelope is 28 mm in diameter and, excluding the B7 base pins, is 81 mm tall.
References: 1040 & 1043. Type HD14 was first introduced in 1940.