The Mazda ECL80 is a triode, output pentode for audio use, it is a low power device with the triode feeding the pentode for a compact single end audio stage.
The ECL80 is a true pentode and the wire grids can be seen through the hole in the anode wall.
The triode shares the common cathode and is mounted at right angles to the pentode axis between the top and middle mica discs.
The thin glass tube envelope is 21 mm in diameter and, excluding the B9A base pins, is 57 mm tall.
References: Data-sheet & 1040. Type ECL80 was first introduced in 1950.