Cylindrical glass vacuum tube with metal interior components and five metal connection pins at the base. The glass envelope is slightly darkened at the tip from use or age. Internal elements—anode, grid, and filament—are visible through the transparent casing.
This radio valve is a standard military replacement component stored within the Case Spare Valves No. 4L (Accession 2020.658). It would have been used in wireless sets and field communications receivers or transmitters to amplify electrical signals.