The CV1090 is an VHF Micropup transmitting triode. It was developed by M-OV as the experimental E1046 and went into service initially as the VT90. It was the first of the Micropup triodes.
The maximum anode dissipation is 100 Watts with forced air cooling. The application was for Radar with peak pulse powers of 5 kW. SeeVT90 for more details.
Clearly the valve is not all there, only the filament and anode remain. The cooling fins have a diameter of 38 mm.
The copper anode tube connects to the external brass cooling fins. In the centre is the filament support and the thoriated tungsten filament is a close wound helix
A closer view.
The glass envelope is 18 mm in diameter and what remains is 68 mm tall.