Sensibly equivalent¶ to:
The HL2 is a dull emitter battery triode. It was designed as a detector in broadcast receivers, in the early 1931 and re-issued as the HL2K in 1934 - same rating but different construction.
We know from the envelope that this was made in England.
The balloon envelope is 40 mm in diameter and, excluding the B4 base pins, is 82 mm tall.
References: Datasheet, 1040 & 1043 Type HL2 was first introduced in 1931.
Absolute Maximum Operating Conditions¶
Updated April 21, 2014. shape:balloon construction:pinch type:triode age:1930.1940 base:b4 heater:2.0v pins:4 pin:1.a pin:2.g1 pin:3.f pin:4.f