The ECL84 is a triode output pentode amplifier designed for class A1 use.
The triode section was designed for a variety of uses including sync separation. The pentode was designed for use as a video output stage. Introduced in 1958 when the UK had a 405 line VHF television service and a video bandwidth of 3 MHz.
The triode on the right and the pentode mounted at right angles.
The pentode with heat radiating fins on the top of the control grid supports.
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 ECL84 was first introduced in 1958. See also1958 adverts.