Sensibly equivalent¶ to:
The Marconi HL210 was first introduced in 1928 and is a general purpose triode.
The dome carries the HL210 Type designation as well as the circular lettering of Made in England.
The etching on the face of the envelope Marconi Valve and has the BVA logo beneath. The anode is positioned horizontally. The grid wire can be seen. The filament is a single strand in a V shape - just as the image in the advert shows.
The balloon envelope is 41 mm in diameter and, excluding the B4 base pins, is 78 mm tall.
References: Datasheet & 1043. Type HL210 was first introduced in 1929.
Absolute Maximum Operating Conditions¶
Updated October 05, 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