The EF184 is a purpose designed high gain frame grid pentode. The EF184 superseded the ubiquitous EF80. The mutual conductance is 15.6 and the closely related (pin compatible) variable μ pentode EF183 has a μ of 12.5.
The Ef184 is a sharp cut-off pentode for use as an IF amplifier in television receivers. This implies a relatively wide band function at about 33 MHz. The high mutual conductance was important for wide band width amplifiers.
The the outer screen is made of solid sheet with holes punched in it. Other EF184 exhibits use an expanded mesh screen.
Here the outer wire grids can be seen including the copper supports of the screen grid.
The thin glass tube envelope is 20 mm in diameter and, excluding the B9A base pins, is 54 mm tall.
References: Data-sheet, 3002 & 1040. Type EF184 was first introduced in 1960. See also 1960 adverts.