The Hivac XSG1.5V is a directly heated battery screen grid valve. Our exhibit is missing its top cap but the XSG2.0V is visually the same and differs only in filament voltage.
The filament is a single hairpin with the top of the loop supported by a spring. The control grid is bright wire wound in the conventional way between support rods. The screen grid is a wire mesh that encircles the control grid in the style of the early screen grid valves. The anode is formed by two small rectangular plates, one on each side of the control grid plane.
This valve would be used in the RF stages of radio equipment operating from dry battery supplies.
The anode is split into two small plates one either side of the grid assembly.
Enlarged the mesh of the screen grid and the zig-zag of the control grid can be seen.
The thin glass tube envelope is 14 mm in diameter and, excluding the Hivac Sm4 base pins, is 61 mm tall.
References: Datasheet & 4002. Type XSG1.5V was first introduced in 1935.