The 1H4G is a battery triode. RCA describe the valve as a low μ device for use as a detector and AF voltage amplifier.
The anode is bright as would be expected in a low power device. The anode is much wider than the front to back dimension as the filament passes up inside the grid as a single inverted hairpin.
Seen from the dome the shaped mica to hold the electrodes in place within the shoulder of the envelope is clearly visible. The grid is held on notched rods on either side. The filament is supported on the top spring. Looking into the valve the characteristic white of the oxide coating can be seen on the filament wire.
The classic envelope is 38 mm in diameter, and excluding the IO base pins is 88 mm tall.
References: Datasheet, 3002 & 1043. Type 1H4G was first introduced in 1936.