The ECL86 was one of the last triode plus output pentode valves designed and was released to the market in 1962. Uses were in domestic radio and audio equipment. Normally in single ended output stages for radio-grams and tape recorders. The design proved popular in low cost stereo systems. The ECL86 was preceded by the ECL82.
The small triode section is on the left and is equivalent to half an ECC83.
The pentode section looking along the axis of the grids. The structure within the anode is the beam plate - this is a beam tetrode.
The thin glass tube envelope is 21 mm in diameter and, excluding the B9A base pins, is 70 mm tall.
References: Datasheet & 1040. Type ECL86 was first introduced in 1961.