The 6AQ8 was the standard double triode for use in the front end stages of FM radio receivers. It was designed specifically for the purpose.
The envelope shows that this exhibit was made in Japan to the CGE specifications.
The two independent valves are screened by a rectangular plate across the diameter of the envelope. One triode would be used as an RF amplifier and the other as the local oscillator. The oscillator would be run 10.7 MHz lower than the incoming signal, and in the mixer a standard 10.7 MHz IF would be produced.
Is was popular in the late 1950s to add an FM radio board to a television receiver as well as to make dedicated Band II receivers.
The side view clearly shows the two separated triodes with the oversized screen between them.
The anode is formed from two sections and the outer surface is carbonised to radiate heat. The anode is made from two sheets, one flat and the other formed to make a rectangular channel for the cathode etc.
A close-up of a single triode showing the copper grid support rods and the grid winding.
The thin glass tube envelope is 20 mm in diameter and, excluding the B9A base pins, is 48 mm tall.
References: Datasheet & 1040. Type 6AQ8 was first introduced in 1954.