The EF183 is a high gain variable μ RF amplifier pentode. It is a late 1950s design and superseded the EF85. The EF184 was the straight version of the design and replaced the EF80. All four valves have the same pin connections.
The screen from the base to the lower mica disc shields the anode connection.
Through the outer mesh screen can be seen the black strap that ties the two halves of the anode together. At full size one can see the open winding of the suppressor grid and the close wound screen grid. But looking closer the flat fine wires of the frame grid can be seen.
A microscope image of the control grid.
The thin glass tube envelope is 20 mm in diameter and, excluding the B9A base pins, is 53 mm tall.
References: Data-sheet & 1040. Type EF183 was first introduced in 1959. See also1959 adverts.