I think you have previously done some research on Prussia and not sure if you are aware of the following extract taken from Iron Kingdom – The Rise and Downfall of Prussia 1600-1947 by Christopher Clark:
In 1730, Frederick William 1 issued a General Jewry Regulation that restricted Jewish trade, forbade Jews to practice in guild-controlled artisan crafts or to peddle wares in the cities, and prohibited them from purchasing houses.
There were further restrictions in 1750, but I would have thought that if the Lietzens/Jacobs were in Glass making at that time, which I suspect they were, this would surely have forced them out. I will investigate further the 1750 restrictions but at first glance they do look as bad as those in 1730[Peter Wales]See ROYAL PRUSSIAhttp://en.wikipedia.org/wiki/Royal_Prussia[Phil Kirby]
More on the Jews in Prussia/Germany.http://www.jewishvirtuallibrary.org/jsource/vjw/germany.html[Phil Kirby]
If you want to know about West Prussia take a look
More resourceshttp://www.his.uni.torun.pl/wydzial/instkat/historia/en/index.html[Phil Kirby]
SEE GENERAL JEWRY LAWS IN PRUSSIAhttp://books.google.com/books?id=GSHNy9qBT0EC&pg=PA13&dq=jews+in+prussia+1750&sig=U7QpNTlwUqWXt-NgQeS9I8m6asE[Phil Kirby]