The 6AT6 amplifier triode with double diodes sharing the same cathode connection was designed for use in superhet receivers for signal detection, AGC rectification and low level AF signal amplification.
The triode anode is blackened, the twin diodes are formed above the top mica.
One of the diode anodes with the triode in the centre.
The thin glass tube envelope is 17 mm in diameter and, excluding the B7G base pins, is 45 mm tall.
References: Datasheet, 3002 & 1040. Type 6AT6 was first introduced in 1946.