Granted Patent
Utility
US 4,386,981 · App. 06/268,591
Method of waterproofing roofs and the like
Inventor:
Allan S. Clapperton
Patented Case
View Patent ↗
Granted: Jun 7, 1983
Filed: May 29, 1981
Inventor
Allan S. Clapperton
Assignee (at issue)
W. R. Grace & Co.
This patent predates the USPTO's electronic file wrapper — prosecution documents from this era exist only in the Patent Office's paper records. A certified copy of the file history can be ordered from the USPTO's paper archives.