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 The EF184 superseded the ubiquitous EF80.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.
In 1969 Mullard describe the valve as: A frame-grid 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. Mullard quote operation at 40 MHz.The logo on the envelope is that of Rediffusion. Rediffusion made television programs and also had a chain of rental shops. Renting equipment was popular in the UK during 1960s and 70s as the reliability of sets was not high - especially valve based colour television. The change came with reliable sets from Japan and the move to solid state products.
The internal coating hides most of the inner structure.
Rediffusion logo on a plain green valve box. The company would buy in bulk and the own branding would both identify the company and deter pilfering.
The thin glass tube envelope is 20 mm in diameter and excluding B9A base pins, is 54 mm tall.
References: Data-sheet, 3002 & 1040. Type EF184 was first introduced in 1960. See also1960 adverts.
