The ER227 is labelled as Everyready Raytheon and is an early American indirectly heated triode. The heater power was ten times that of the directly heated triode it was based on and grid emission resulted.
The anode is constructed from mesh.
The mica support is elaborately shaped and held in place with small clips.
Seen from the underside the heater enters the cathode that is filled with insulation. The spiral grid is wound on two supports.
The balloon envelope is 44 mm in diameter, and excluding the UX5 base pins is 96 mm tall.