It might help to have a potted idea of the history of Europe in the 19th century. Until the end of WW1 central Europe was divided up between three great empires - German, Russian and Austro-Hungarian, the borders of all three meeting in Poland/Ukraine(more or less!). East Prussia was one state in the kingdom of Prussia which was in turn the largest state in the German empire, so Amelia would have come from East Prussia in Prussia in "Germany" - same difference - and their citizenship/nationality would be German but their ethnicity obviously Jewish. Although there would have been many Polish Jews of German nationality in these areas I would say that the names point to them being German Jews, not Polish. Those are definitely German names. However there is one more point which should perhaps be kept in mind. Jews were forced to take Europeanised names in the 18-19th centuries and in many cases took the name of a local physical place, e.g. Grunewald = Greenwood/forest, Sternberg = Star mountain or the name of a locality, Berliner, came from Berlin. For this reason I would consider that Pincus might possibly have come from Slovakia originally. Pressburg was the Austro-Hungarian name for Bratislava, which was a quite important garrison town. A Jew from Pressburg could easily have taken the name of Pressburger when he was required to Europeanise his name because he lived in Pressburg. In this case he would have been an "Austrian" citizen/nationality even if he had originally been a "German" Jew. Even if that turns out to be right I think you can accept that Emilia was German, Neustadt could easily have been adopted because they lived in the "Neustadt" (New Town) of some bigger place. Would suggest you google up a map of 19th century Europe and orientate yourself - at least East Prussia will show up clearly. Hope this helps a bit.