The 6Q7GT is a commercial double diode triode 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. This is a miniature glass tubular version of this valve.
The base carries identification and the makers name. The envelope also carries an etched type identification. The triode anode is at the top of the envelope, it is blackened to radiate heat and the side fins are also part of the heat management.
The diode anodes are L shaped and sit either side of the common cathode and below the triode. They are left bright as they dissipate very little heat as signal detectors.
The wide glass envelope has a maximum diameter of 29 mm and a length excluding the IO base pins of 69 mm.
References: Datasheet, 1040 & 1043. Type 6Q7GT was first introduced in 1936.