The 6AT6 amplifier triode with double diodes sharing the same cathode connection was designed for use in superhet receivers as detector, AGC rectifier and first audio amplifier.
The triode is close to half an ECC83 and works well as an audio voltage amplifier.
The twin bright arch pieces that are the diode anodes are a defining visual feature of the 6AT6. The CBS logo.
These look like after market stamps.
The thin glass tube envelope is 17 mm in diameter and, excluding the B7G base pins, is 47 mm tall.
References: Data-sheet, 3002 & 1040. Type 6AT6 was first introduced in 1946. See also1946 adverts.
