Granted Patent
Utility
US 4,948,647 · App. 07/308,922
Gypsum backer board
Inventor:
Edward A. Burkard
Patented Case
View Patent ↗
Granted: Aug 14, 1990
Filed: Feb 13, 1989
Inventor
Edward A. Burkard
Assignee (at issue)
National Gypsum Company
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.