The 41MHL is an indirectly heated triode and was suitable for detector or audio amplifier in a radio receiver. Internally the valve has both a control grid and a screen grid. The latter is internally connected to the anode by a length of coiled wire.
The anode consists of a box support with a mesh centre to each working face.
The insulated heater wires can be seen entering the oxide coated cathode. The anode connects internally to the screen grid.
The internal construction. The screen grid is connected internally to the anode. The control grid is wound on two notched rods but has been crimped so as to form the grid around the central cathode tube.
This image shows the grid formation.
The balloon envelope is 50 mm in diameter, and excluding the B5 base pins is 106 mm tall.
References: Datasheet, 1043, 3002 & 1040. Type 41MHL was first introduced in 1930.