The CV784 is a diode pentode valve that was designed for battery portable radio receivers and is identical to the commercial 1S5.
The KB/EN identifies this valve as being made to specification K1001 or K1006, the B denotes qualification by a UK authority and the EN identifies the maker as Thorn-AEI, Sunderland.
The filament leaves the top mica and then passes through a small flag-like piece of metal. This is the single diode.
The diode end on has a small separation between the sides.
The thin glass tube envelope is 18 mm in diameter and, excluding the B7G base pins, is 47 mm tall.
References: Data-sheet & 1040. Type CV784 was first introduced in 1947. See also1947 adverts.
