Cylindrical miniature radio vacuum tube made of clear glass with a visible internal electrode assembly and five protruding metal pins at the base. The top of the tube is slightly tapered with a sealed tip. Markings are minimal, indicating a production or testing series rather than full manufacturer branding.
This valve was part of a military spare parts kit (Case Spare Valves No. 4L, Accession 2020.658) and would have been used to replace damaged or failed tubes in field radio or wireless communication units.