The Z14 is a variable μ RF pentode for dry battery operation used for domestic broadcast receivers at RF or as an IF amplifier. The filaments had to have the lowest possible consumption due to the cost of the dry batteries.
This exhibit carries the M-OV identification lozenge but was later sold by The Bentley Acoustic Corporation as per the paper label.
The screening makes a view of the electrodes difficult. Here the three wire grids can just be seen.
The rods rising from the outer edges of the pinch are the anode supports the visible cylinder is the shield as is the bright plate below the grids.
The control grid connects to the top cap. The fine wire running from the lower shield support to the centre of the valve is the filament tension spring and one of the filament connections. The oxide coated filament can be seen as a single strand entering the valve between the control grid supports.
The wide glass tube envelope is 29 mm diameter, and excluding the IO base pins, is 81 mm tall.
References: Data-sheet, 1040 & 1043. Type Z14 was first introduced in 1940.