The FC2A as a two volt battery mixer or frequency changer and first appeared in 1937 it was later known as the KK32 when issued on an octal base. The design is as an octode and Mullard describe the operation as a triode oscillator followed by a pentode mixer, but in one single electron stream. By the late 1930s the two volt battery valves were displacing the four and six volt versions.
This example has had half of the external metalising paint removed allowing a view of the construction.
The top components. The filament can be seen and is clearly oxide coated.
There are six grid supports and the second looks to be a pair of stout wires. This would be the oscillator anode. The outer grids are thin wire and circular in shape.
With the screens it is difficult to get a clear shot of the grids.
The classic envelope is 44 mm in diameter, and excluding the B7 base pins is 112 mm tall.
References: Datasheet & 1043. Type FC2A was first introduced in 1937.