To return to an earlier topic:

As Jim Gibb mentioned, Alan Gilbert at Fordam University has been
collecting and analyzing marked bricks for a number of years.  His 1993
article in the SHA journal explained the methods he is using.  He has taken
samples of redwares from all of the major New York City projects and from
some sites in Philadelphia, Boston, and New Jersey as well as the
Netherlands.  Alan has been amassing data over the years and has given
papers, alone and with others, on various brick and redware sourcing
topics.  His research will eventually be synthesized in a major
publication.  Meanwhile here is the basic reference:

Gilbert, Allan, Garman Harbottle, & Dan deNoyelles,
1993  A Ceramic Chemistry Archive for New Netherland/New York. Historical
      Archaeology 27(3):17-56.