Logan Kleinwaks alerts us to an incredible find - there is a 
reproduction of a map "identifying 77 Jewish property owners and 
their properties in Plock, Poland in 1803.  [A version of it] has 
been provided as a special exception, by the Biblioteka 
im.Zielinskich Towarzystwa Naukowego Plockiego.  To download the map 
image and a spreadsheet with [Logan's] transcription of the property 
owners' names (most with patronymics, not fixed surnames), and for 
more details about the source, visit 
http://genealogyindexer.org/forum/viewtopic.php?f=2&t=3190."
Thank you Logan!