This X41 is an unmetalised or clear triode hexode frequency changer designed for AC mains receivers. The X31 was designed with a heater for universal mains (AC/DC sets) but is otherwise identical. Other other X41's have metal paint screening applied.
The Marconi paper label. Osram valves would differ only in the label applied at the end of production at M-OV.
The B7 base pins, pinch and lower mica.
The insulated heater is helically wound before inserting into the round cathode tube.
The classic envelope is 44 mm in diameter and, excluding the B7 base pins, is 118 mm tall.
References: Data-sheet & 1043. Type X41 was first introduced in 1935.