The 6F19 is described as a VHF variable-μ pentode, this places the valve in a superhet context with AGC applied to the RF and IF sections. It was a television valve and the frame grid valves overtook its performance.
Inside the perforated screen can be seen the wire grids and the strap connecting the two halves of the anode.
Made in England.
Through the hole in the screen can be seen the helical suppressor grid and within the shaped screen grid with the wire passing flat across the cathode. The control grid can just be glimpsed.
The thin glass tube envelope is 21 mm in diameter and, excluding the B9A base pins, is 59 mm tall.
References: Data-sheet & 1040. Type 6F19 was first introduced in 1959.