If you look under "Kartenmeister" you will find you can put in as little as the first letter of a town/village and the province Ostpreussen and it will throw up everything starting with that letter. There was a Hartwichs in Pruessisch Holland, Ostpreussen which is now Bukowa in the Polish province of Elblaskie, ca. 3.4km from Grunhagen, nowadays Zielonka Paslecka There was also a Hartwich Vorwerk (this last word puzzles me as it does not really sound like a place name - but!). This was in Mohrungen, Ostpreussen and is nowadays Warkalki in Olsztynskie Province in Poland about 4 km from Gross Hermanau, today Niebrzydowo Wielkie in Poland. What is particularly interesting about this site is that when you have pinned down your town there is an opportunity to email other people who are interested in the same place, which might lead anywhere. Hope this helps.