The 6SN7GT is a small glass tubular audio double triode. This was a classic design with two separate triodes in the one envelope. The 6SN7 remains the most popular Octal based double triode valve for audio applications. The valve is especially well suited to phase splitter designs.
The envelope carries the word 'foreign' and the anode construction matches the American pattern. UK made versions had wide anodes as in the Brimar 6SN7GT.
One anode looking at right angles to the grid. The centre of the working face is where the cooling/fixing flange is placed.
The anodes looking along the grid axis. Note the heat sinking fins on the grid supports. These fins are absent on the UK made valve.
The wide glass tube envelope is 28 mm in diameter and, excluding the IO base pins, is 68 mm tall.
References: Data-sheet, 3002 & 1040. Type 6SN7GT was first introduced in 1941.