You should also check the following comprehensive reference on this subject:
Roenke, Karl G.
1978 Flat Glass: Its Use as a Dating Tool for Nineteenth Century
Archaeological Sites in the Pacific Northwest and Elsewhere.
Northwest Anthropological Research Notes, Memoir No. 4.
(University of Idaho, Moscow series).
This was a thesis done by this person which was published in this series
which should be available in any good research library.
Mike Polk