The DE5 is a dull emitter triode designed to be used as an audio output valve to drive small loud speakers. The DE5 developed into a family with DE5A and DE5B as well as the original DE5 valve.
The gettering on this exhibit has turned slightly milky, suggesting that the valve is now soft i.e. poor vacuum. There is no pip top on this valve the evacuation tube has been moved to the pinch stem and base. This contrasts with some of our other DE5 exhibits.
The electrodes are indistinct when seen through the milky haze. DE5 has a much clearer view.
The lettering is on the dome but is very faint. The grid, filament tension spring and anode can be seen in this image.
The balloon envelope is 50 mm in diameter, and excluding the B4 base pins, is 106 mm tall.
References: 4051 & 1003 Type DE5 was first introduced in 1924.