This version of the first thermoinic device for communication use has a candelabra base. and on the envelope is the makers name. Fleming Oscillation Valves were first made by the Edison Swan company.
Fleming has a bayonet base as used in light bulbs. Fleming named the device the Oscillation Valve as it had the function of passing only the positive half cycles of the incoming RF signal and thus made it possible to hear the signal in headphones.
Fleming originally used carbon filaments running at 12 Volts. Later versions of his Oscillation Valve ran at 4 Volts.
Fleming used the Edison effect to rectify RF signals in wireless telegraphy. Power rectification was developed independently by Wehnelt in Germany.
The anode cylinder is connected to the outside by a wire passing through the side of the envelope. This exhibit has a different anode material to Fleming.
The lettering is etched into the glass. The name Ediswan can be seen as can the words Oscillation Valve. The filament voltage seems to read 8 but this is probably a badly formed S with the actual voltage indistinct.
The glass can be clearly seen to protrude through the anode. The metal is grey but it is not clear what material this is. The bright wire connecting to the side wire is probably platinum.
The wide glass tube envelope is 32 mm in diameter, and including the base is 81 mm tall.
References: 1047 & Observation. Type Fleming was first introduced in 1904.