Economic Electric first introduced the Xtraudion bright emitter in about 1923. A year later the dull emitter version the Dextraudion appeared. Their electrode shapes differ from the Cossor P1 or the R-type probably to avoid patent infringements.
The damaged lettering looks to read 1V - 0.1A, 20 - 60 V with a serial number below.
The plated base cap and simple split pins.
The long pinch stem and box electrodes above.
Face view with all three electrodes held at two points.
The single strand filament is held in folds of the supports at either end.
The anode is an open box and within the grid is a series of flat topped U wires welded to support rods on either side.
A closer look.
The wide glass tube envelope is 30 mm in diameter, and excluding the B4 base pins is 72 mm tall.
Reference: Valve Box. Type Dextraudion was first introduced in 1924. See also1924 adverts.
