Type 6N7 is by no means a general-purpose double triode since it has a powerful heater, a common cathode, and is designed to operate in push-pull Class B2 with zero grid bias or quiescent push-pull. The anode to anode load is given as 8,000 Ohm.
It is specifically an audio power valve capable of 10 W output.
Thanks to Bob Hopkins for sending the image.
The classic envelope is 42 mm in diameter and, excluding the IO base pins is 82 mm tall.
References: Datasheet & 1043. Type 6N7G was first introduced in 1936.