The 6Q7G is a double diode triode and was designed for receiver audio use.
The diodes would be for signal and AGC rectification and the triode would act as AGC amplifier or first audio amplifier.
The classic envelope is 37 mm in diameter and, excluding the IO base pins, is 94 mm tall.
References: Data-sheet, 1040 & 1043. Type 6Q7G was first introduced in 1936. See also 1936 adverts.