Marconi Radio Valve Type R, by Marconi Company, English, c. 1916

Marconi Triode Radio Valve Type R, with slightly smoked glass, a concentric formation of electrodes, and a single fine strand of tungsten filament. The fragile and brittle filament has been partly protected by a coil formation adjacent to the clearly visible grid support, giving a measure of tension to prevent sag when the filament is at operating temperature. The pin formation suggests a date of production during WW1. With nickel-plated base and four steel? base pins. Previously catalogued with three other Type R Radio Valves (Inv. Num.s 22908, 82041, 80773).