McVitie Weston valve collection, STC Micromesh valve, type H.L.B.1
STC Micromesh valve, type H.L.B.1, glass envelope metallized, (RMW/D89 - McVitie Weston number), by Standard Telephones and Cables Limited.
STC Micromesh valve, type H.L.B.1, glass envelope metallized, (RMW/D89 - McVitie Weston number), by Standard Telephones and Cables Limited.