The WD40 is a vari-μ RF pentode and a pair of single diodes all sharing a common cathode and fitted with a B9 base cap. It was designed for all AC mains radios and the heater is the then UK standard for indirectly heated valves at 4.0 Volts at 1.0 Amps.
The WD30 was designed for use with series heater chains operating at 300 mA and was released in 1935.
The Marconi brand printed onto the zinc metal screening paint that has started to peel off.
Reference: 1043. Type WD40 was first introduced in 1935.
Absolute Maximum Operating Conditions¶
Updated July 21, 2020. shape:classic construction:pinch type:double.diode.pentode age:1930.1940 base:b9 heater:4.0v pins:9 pin:1.h pin:2.k.g3 pin:3.a(d1) pin:4.a(d2) pin:5.m pin:6.g2 pin:7.a pin:8.- pin:9.h pin:tc.g1