The Marconi P215 is a directly heated triode. Etched faintly on the side of the glass are the words Marconi Valve and there is also the BVA logo.
The etched lettering on the dome gives the P215 identification as well as Made in England and Protected by Patents.
Reference: Datasheet. Type P215 was first introduced in 1930.
Absolute Maximum Operating Conditions¶
Updated January 17, 2018. shape:balloon construction:pinch type:triode age:1920.1930 base:b4 heater:2.0v pins:4 pin:1.a pin:2.g1 pin:3.f- pin:4.f+