This valve is a repaired triode from the 1920s. The filament is rated at 3 - 5 V at 0.25 Amp. The anode is rated for use between 45 and 120 Volts.
A number of small firms repaired valve filaments during the mid-1920s but all repaired samples we have seen have a circular cut mark on the envelope which is not see in the Photo. The paper label attributes this valve to GWI limited, who made their own valves (several types) for a couple of years around 1925/26. However, most known GWI valves have black bakelite base caps.
The shape of this exhibit is similar to the Mullard ORA series but only the ORA DF (we believe) was gettered. As far as is known all repaired valves were 'brights' since the back-yard firms that did the repairs did not have the equipment or the technology to do 'dulls' successfully. GWI, however, did make and market some 'dulls'.
The balloon envelope is 34 mm in diameter and, excluding the B4 base pins, is 78 mm tall.
Updated January 21, 2013. shape:balloon construction:pinch type:triode age:1920.1930 base:b4 pins:4 pin:1.a pin:2.g1 pin:3.f pin:4.f