The CV466 is a sub-miniature wire ended sharp cut-off general purpose indirectly heated pentode. The prototype was the VX8046 and commercially it is the Mullard EF73. Sub miniature valves such as this appeared in the USA in the late 1940s and were first produced in the UK by Mullard in 1950 at a specialist manufacturing facility.
The outer two grids can be seen here and are helical in form. The control grid is of a finer pitch and passes flat across the cathode.
The wire leads emerging from the hard glass base. The geometry is called the B8D/F base.
The thin glass tube envelope is 9 mm in diameter, and excluding the base wires is 37 mm tall.
Reference: Datasheet. Type CV466 was first introduced in 1950.