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.
The electrodes are mounted a considerable distance from the pinch in this valve.
The 6 can just be made out on the glass as well as part of the L.
The classic envelope is 51 mm in diameter and, excluding the IO base pins, is 117 mm tall.
References: Data-sheet, 1040 & 1043. Type 6L6G was first introduced in 1936. See also1936 adverts.
