In 1807 Napoleon's youngest brother Jerome, became King of Westphalia and he ruled till 1813. During this time, Jews had to take a second surname because many of them had the same name but not all Jewish families kept those names after Jerome's rule. Some families went back to the old names. So you can find the name Katz-Weinstock in Guxhagen, only in the lists of 1812. In the later births, marriages and deaths lists which were written by the Jewish community of Guxhagen you can't find the name Weinstock again, only the name Katz.