The CV782 (commercially the 1R5) is a miniature heptode frequency changers. The valve design was for dry battery operation.
The KB/E identifies this valve as being made to specification K1001 or K1006, the B denotes qualification by a UK authority and the E identifies the maker as Thorn-AEI, Brimsdown.
The bright anode and above and below it can be seen the many grid supports and fine grid wires. The filament is a single vertical strand that passes vertically through the electrodes but is moved at the top through a small angle by the hole in the top mica to connect to the tension spring.
From the top the filament can be clearly seen as can the wire grids with support rods aligned in two axis.
The thin glass tube envelope is 18 mm in diameter and, excluding the B7G base pins, is 44 mm tall.
References: Data-sheet, 1040 & 1043. Type CV782 was first introduced in 1947. See also1947 adverts.
