The RCA 8011 radar power triode was designed for 300 MHz (100 cm) operation in pulse mode. The VT90 was the original 'micropup' from M-OV that made airborne Radar a practical proposition and this exhibit carries both Type designations.
The VT90 was developed from the DET12 first as a co-axial version of the original valve with a Type designation of E1029 and later as the E1046 it produced pulses with a 5 kW peak power.
The construction is co-axial and the anode is finned to enable forced air cooling. The grid is connected to the pin at the right in the picture. The filament connects at the left and the finned anode is seen at the centre.
These valves that were developed for military applications prior to the outbreak of war had no commercial use or Type designation.
The UK Navy used M-OV 'micropups' in their type 284 fire control radar that operated at 600 MHz.
The VT90 was used in the AMES11 and AI radars.
The anode connection would be made to the ring on the left of the fins. The stranded filament leads are permanently connected to the rods coming through the glass/metal seals.
The grid end where only the end cap of the cage can be seen. Internally the filament is a helix and the grid is in the form of a 'squirrel cage' with a cylinder of equi-spaced wires mounted between two end plates.
The thin glass tube envelope is 18 mm in diameter and, including the base, is 124 mm long.
References: 1005 & R J Sutherland Type 8011 was first introduced in 1939.