The 6SQ7GT/G is a double diode triode. The diodes are for AM signal detection and AGC detection whilst the triode section is for first audio amplification. This is typical for a valve used in a radio superhet receiver.
The triode is at the top with the diode anodes housed in the bright screen below.
The wide glass tube envelope is 28 mm in diameter and, excluding the IO base pins, is 64 mm tall.
References: Datasheet, 1040 & 1043. Type 6SQ7GT was first introduced in 1939.