The E4N is an early transmitting triode. The twin top caps connect to the grid and the anode. The aim being to get maximum isolation between input and output circuits. It looks as if the envelope is 85 mm in diameter and that the valve is 170 mm tall based on the diameter of the base cap. The single strand filament is probably Tungsten and so a bright emitter the filament rating supports this.
Many thanks to Antonio Creus for sending these images.This valve sold in 2010 for 400 Euros.
The detail of the construction. The grid and anode are both supported on glass rods surmounted by a glass bead, these rods slide into tubes fixed to the pinch. The grid helix is held in place with two wires woven between the turns.
The balloon envelope is 85 mm in diameter, and excluding the B4 base pins is 170 mm tall.
Absolute Maximum Operating Conditions¶
Updated April 27, 2013.