I have seen this mark incorrectly identiified as [i]Rhenania[/i] a few times before.

Note the initials W-D-P in this context: [b]Westdeutsche Porzellanfabrik Duisdorf GmbH[/b] from the city of Duisdorf near Bonn, Germany. This company existed 1904 until 1935 [b]before[/b] it became the [b]Porzellanfabrik Rhenania GmbH[/b] (1935 until 1957).