This valve is clearly a power amplifier designed for VHF and above. The anode fins indicate that forced air cooling was required.
The central anode with threaded holes for mounting. A considerable blast of air would be required and a special base with chimney would have been designed for this valve.
The heater connections. The holes also suggest forced air cooling at this end to keep the glass/metal seal cool. The two rings are either cathode and control grid or control and screen grid. Nothing of the internal structure can be seen to confirm whether this is a triode or tetrode.
A closer look at the side rings.
The planar envelope is 47 mm in diameter and, including the base pins, is 109 mm tall.
Updated April 10, 2021.