This exhibit is a new old stock generic 5Z4G full wave rectifier. Professional equipment, including radar, etc., sometimes required circuits in which valve cathodes carried large signals and had to 'float' at voltages well below that of the chassis. Glass-envelope '-G' versions of common types were therefore required.
Designed to supply equipment of up to 40 Watts total power, this rectifier was made by several manufacturers. This suggests a very popular type, and one that found use in military equipment during WWII.
Every maker had their own arrangement of anodes for the 5Z4G and in this example the anode is an + shape.
The heater wires are well insulated and coiled together.
The classic envelope is 39 mm in diameter and, excluding the IO base pins, is 91 mm tall.
References: Datasheet & 1043. Type 5Z4G was first introduced in 1940.