The CV2983 is the UK Government specification for DL94 audio output pentode. Mullard describe the DL94 as a battery operated output pentode with centre tapped filament, and designed for operation with equal voltages on both screen and anode.
At the lower part of the envelope can be seen the words Made in Italy.
The filament tension spring can be seen at the top.
The filament is four vertical strands with the top loops held under tension.
The thin glass tube envelope is 18 mm in diameter and, excluding the B7G base pins, is 46 mm tall.
References: Data-sheet, 1040 & 3002. Type CV2983 was first introduced in 1956. See also1956 adverts.