The CV8634 (commercially the ECL83) is an audio triode pentode designed for single ended audio application such as TV audio and the commercial Type was much used in domestic record players.
With an anode load of 7,500 Ω this valve delivers its modest 2.5 Watts. This in the 1960s was the standard output for low cost audio products.
The CV8634/ECL83 is quite short compared to the ECL82 and ECL86.
There is no maker details on the envelope but the typeface is commonly found on Mullard valves.
A true pentode with three wire grids. The triode sits parallel to the output section.
The supports of the three grids and the cathode tube above the top mica.
The thin glass tube envelope is 20 mm in diameter and excluding the B9A base pins it is 48 mm tall.
References: Data-sheet & 1040. Type CV8634 was first introduced in 1957. See also1957 adverts.