The 6SL7GT is a medium impedance double triode with a gain of 70. It was designed for voltage amplification in audio amplifiers and/or as a phase inverter.
Unlike most of our Zaerix branded valves this exhibit is clearly marked as being Made in Russia.
The two sections seen from the side.
In face view the triode sections can be seen to have fixings and cooling flanges mounted towards the outside of the envelope.
Here is another Zaerix 6SL7GT of identical construction but without a country of origin marked on the valve.
The wide glass tube envelope is 28 mm in diameter and, excluding the IO base pins, is 62 mm tall.
References: Data-sheet, 1043, & 1040. Type 6SL7GT was first introduced in 1942. See also1942 adverts.