The 6L6G is is a larger more powerful audio beam tetrode than the 6V6 receiver type. This was used for audio amplifiers and modulators for small Amplitude Modulated transmitters.
Traditionally the 6L6G was housed in the classic or shouldered envelope and the 6L6GT version was in the small glass tubular envelope. This exhibit is marked by Brimar as a 6L6G but is the same size as our 6L6GT.
Sadly British policy was to have imports marked with the pejorative 'foreign'.
The anode extends sideways to give greater radiating surface area and the two halves are stitched together.
The four side micas hold the electrodes rigid in the glass.
The wide glass tube envelope is 34 mm in diameter and, excluding the IO base pins, is 93 mm tall.
References: Datasheet, 1040 & 1043. Type 6L6G was first introduced in 1936.