The dull emitter Cossor P3 was designed as an audio amplifier and output valve. The anode is a more pointed shape than the P1 and P2 bright valves but the internal construction is different.
The paper Cossor label is present in addition to the Cossor name on the glass.
Patent information.
The base cap with simple split-pin brass pins and a hollow centre. The wires are soldered to the tops of the pins.
The etched Cossor name on the right and the Type designation on the left. Very feint.
The filament tension spring passes through a ceramic insulator in the top of the anode. The fact that it is not in contact with the insulator shows that the filament is open circuit.
A glimpse of the lower end of the anode. The filament support has a wire attached and round the wire is a larger diameter - probably the oxide coating.
The balloon envelope is 45 mm in diameter and, excluding the B4 base pins, is 100 mm tall.
References: Data & 1043. Type P3 was first introduced in 1925. See also1925 adverts.
