This 6H6GT from Brimar has a squat pinch construction and a top mica to firmly hold the twin diodes in the envelope.
The original American metal 6H6 was introduced in 1936. The glass tubular versions appeared in 1940 and by virtue of using the older pinch technology are larger than the glass disc constructed metal valve.
The side view shows the very thin structures. The centre plate is the screen.
Face on the detail can be seen. The working space is the central cylindrical space in the bright anode. The two plates forming the anode are stitched together and form cooling fins and the lugs locate the anode in the mica supports. The central cathode is heated by the insulated hairpin heater. The tungsten heater is probably tightly coiled within the insulation.
The wide glass tube envelope is 29 mm in diameter and excluding the IO base pins the valve is 47 mm long.
References: Datasheet, 1040 & 1043. Type 6H6GT was first introduced in 1940.