The EDD11 is a double triode audio output valve that can deliver 5.5 Watts when used with an anode to anode load of 16,000 Ω.
We have the complete line-up of valves from the set this valve was used in. Frequency changer ECH11, IF amplifier EF11 x 2, demodulator, AGC detector and first audio stage EBC11, push-pull audio output EDD11 and rectifier EZ11.
The identification was painted into the dome.
The plastic spigot has broken off and the copper evacuation tube is visible. Note that it is sealed with solder.
Another view of the evacuation tube.
The wide metal tube envelope is 36 mm in diameter, and excluding the footless base pins is 42 mm tall.
Reference: Data-sheet. Type EDD11 was first introduced in 1938. See also1938 adverts.