The 6CW4 Nuvistor from RCA is a triode for use at VHF and built into a small metal case. The base is ceramic sealed to the metal case and five fine pins, on a 12 pin grid, form the connections and the electrode supports internally.
The Nuvistor is built as a series of co-axial electrodes but they are all very small, and small inter electrode capacitances result. Thus the high frequency of operation. Unlike the transistors of the time the Nuvistor had the overload and intermodulation characteristics of the valve, superior to the transistor.
The RCA name as well as the trade name Nuvistor. the pins can be seen as copper wires.
The Type designation on the top of the can.
The ceramic base: some wires act as pins and the rest are cut off at the base and form the internal fixing points.
The thin metal tube envelope is 9.4 mm in diameter and, excluding the fine base pins, is the 20 mm tall.
Reference: Data-sheet. Type 6CW4 was first introduced in 1960.