This part is a kind of semiconductor called EL36.

Function of this product has Output Pentode.

Manufacturers : Mullard

Image and pinout :

Some of the text within the PDF file :

Note by FP: This Mullard EL36 was the EL6 with Octal base. Later the EL36 became the Line Output Pentode, the 6.3V version of the PL36. [ ... ]

EL36 PDF Datasheet Download