The 6K7G is a screened pentode and was designed for intermediate frequency amplifiers in superhet receivers. It is high impedance type allowing for a high Q in the tuned anode circuit.
The etched ellipse containing the Type designation is typical M-OV.
The Type is also printed on the glass together with the up-arrow for UK Government procurement.
Within the top screen can be copper supports for the control grid with the connection to the top cap. The cathode tube is round and below the top screen can be seen the wire grids.
The three wire grids and their relationship to one another and the central oxide coated cathode.