Yes a Neudruck is an official reprint usually from the original plates.
But a Nachdruck is basically a copy or fake which is similar to the original but in fact is no such thing.
See here in the German Wikipedia. http://de.wikipedia.org/wiki/Neudru...hilatelie%29
Neudrucke kann es auch postalisch korrekt verwendet geben, Nachdrucke sind immer Fälschungen.
Loose translation Some Neudrucke/reprints can also be used as proper postage,
Nachdrucke are always fakes.
I can't be certain because of the poor scan but
the stamp above looks like it was printed either by typography
or lithography not engraved as the original.
If it would be a reprint by the Reichsdruckerei
they would have used engraved plates.