The 6SQ7GT is a double diode triode sharing a common cathode.
The triode is seen at the top with the carbonised anode, the double diodes are seen as the anodes between the triode and the pinch. In this valve one diode anode is the enclosed box and the second diode anode is a pair of vertical rods
The clamping metal shell that covers the envelope/base junction has sprung loose.
This valve was designed for superhet receiver use where the diodes would act as signal detector and AGC detector and the triode would be the first stage audio amplifier.
The shell has sprung loose and most of the brown cement has broken away. This valve was new old stock and not opened until wanted for photographing. This is a non UK made valve labeled as Foreign.
The triode at the top and the diodes below seen end on.
The triode grid winding is not visible and the diode anodes
The wide glass tube envelope is 28 mm in diameter and, excluding the IO base pins, is 68 mm tall.
References: Datasheet, 1040 & 1043. Type 6SQ7GT was first introduced in 1939.