The 2C43 is a planar triode that is also known as a Lighthouse valve because of its shape. The 2C43 is designed as an RF oscillator and class C RF amplifier but can also be run as a class A amplifier. The design frequency range is likely to be UHF.
The base shell is the RF cathode connection. The first ring is the grid connection and the top cap is the anode.
The GE manufacturers logo. The American General Electric.
The essence of these UHF valves is a flat cathode placed very close to a mesh grid that extends right across the valve. The other side of the grid is a flat topped cylinder anode. In use the valve is mounted into a two chamber cavity. The cathode forms part of the lower wall and is clamped by the base shell. The grid is aligned so as to be continuous with the centre plate of the cavity. The anode passes through the top plate.
The planar envelope is 12.25 mm in diameter, and excluding the IO base pins is 53 mm tall. The top cap diameter is 9.5 mm, Grid ring 12.25 mm, cathode ring 17.75 mm, base rings are 26 mm (metal) and 32 mm (plastic).
Reference: Datasheet. Type 2C43 was first introduced in 1945.