Granted Patent
Utility
US 4,455,271 · App. 06/462,755
Foamed gypsum wallboard
Inventor:
Robert M. Johnson
Patented Case
View Patent ↗
Granted: Jun 19, 1984
Filed: Feb 1, 1983
Inventor
Robert M. Johnson
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.