The DN143 is a double diode audio output pentode, and very few detector/output valve were designed. This valve carries the Marconi paper label but was made in Holland. Thus it was made by Philips and so is identical to the EBL21.
The valve has a common cathode and the diodes are for signal rectification for detector or AGC service. Simple broadcast receivers for local station reception of strong signals would be the application.
Made in Holland.
At the base are two small plates either side of the cathode that act as the diode anodes.
The anode is black for good heat radiation. The control grid has heat sink fins at the top.
The wide glass tube envelope is 27 mm in diameter, and excluding the B8B base pins is 75 mm tall.
References: Datasheet, 1040 & 3002. Type DN143 was first introduced in 1947.