This exhibit is an early EL41 with a metal skirt. Later production EL41's used a moulded pip in the glass for correct location in the valve holder.The EL41 is an all glass output pentode rated for 9 Watts anode dissipation, and intended for use in AC mains operated equipment. The EL41 should only be used with self-bias or semi-automatic bias.
The control grid is fitted with cooling fins.
The extended copper supports to the control grid connect to the radiating fins. The other grids can be seen through the notch in the anode.
The thin glass tube envelope is 20 mm in diameter and, excluding the B8A base pins, is 70 mm tall.
References: Datasheet & 1040. Type EL41 was first introduced in 1947.