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 Brimar.
The original 6X5 design dates from 1936 but the Brimar type appeared in 1940.
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 picture shows the two anodes stacked vertically on the common cathode tube.
We have a second Brimar 6X5GT and this shows a different form of construction.
The valve features a common cathode cylinder and two separate anodes, but in place of the anodes being stacked vertically in the same plane the second form has the anodes set at right angles to one another.
This cross shape allows for each anode to have a full length section and a half height compartment surrounding the cathode. This clearly gives a larger surface area per anode but uses less total height. Thus contributing to a more robust and compact design.
The wide glass tube envelope of the top valve is 28 mm in diameter and excluding the IO base pins the valve is 70 mm tall.
References: Datasheet, 1040 & 1043. Type 6X5GT was first introduced in 1936.