This version of the first thermoinic device for communication use has a candelabra base. 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.
The open end of the cylinder shows how the thin sheet metal overlaps. Initially platinum was used for the anode but later aluminium was used.
The opening in the side of the anode appears to have glass from the lower support within. This would both hold the anode in place and allow the filament to be seen.
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.