The WR1 from Cossor dates from 1924 and is a dull emitter triode with a built-in filament resistance of 8 Ohms. The filament is oxide-coated.
Cossor had introduced dull emitter replacements for their earlier valves in the form of the W1 and W2. This valve was made to ease the transition from the six volt filament supply for bright emitter sets to the two volt LT supply for the dull emitter valves. The advertising literature stated that when all the bright emitters had been replaced, the screw could be moved and the set immediately operated on the more economical two volt accumulators.
This exhibit does not have a Type designation present on the glass but it has a clear envelope as does the W1 whereas the W2 and hence the WR2 has a red paint applied to the top.
The resistance wirre is sited in the groove under the tape. The shorting screw has two positions - one being a dummy ie non shorting, to keep the resistor in circuit. The lettering on the base shows which positions have what effect.
The base showing the embossed lettering for the two position shorting screw as well as anode and grid.
The 'top Hat' anode with the fan shaped grid within.
The wide glass tube envelope is 28 mm in diameter and, excluding the B4 base pins, is 79 mm tall.
Reference: 1003. Type WR1 was first introduced in 1924.