The 5A/163K is an HF pentode with a high mutual conductance and high anode current. The high current would aid in the attaining of a low noise figure. The valve, as a CV1635, was used by the UK GPO.
The CV Type designation. The F identifies the factory as STC, Paignton (Devon).
The mesh breaks up the image but the two small active anode plates can be seen joined by a strap.
The thin glass tube envelope is 21 mm in diameter, and excluding the B9A base pins is 46 mm tall.
References: Data-sheet & 1040. Type 5A/163K was first introduced in 1956. See also1956 adverts.
