The 6X5GT is a standard HT rectifier for low power AC mains driven equipment. It was of a type made by several manufacturers, in this case Tung-Sol in the USA.
The output of a centre tapped transformer would be applied to the anodes, the rating given is 325-0-325, the common cathode would be the output for the rectified voltage. A effective series resistance of 350 Ohms was required to limit surges and the reservoir capacitor had to be restricted to 16 µF.
The pair of anodes are placed either side of the common cathode and this makes a very slim design.
The anodes are blackened on the outside to radiate heat away. The inside surface is plain bright nickel sheet.
The wide glass tube envelope of the top valve is 29 mm in diameter and excluding the IO base pins the valve is 58 mm tall.
References: Datasheet, 1040 & 1043. Type 6X5GT was first introduced in 1936.