Granted Patent
Utility
US 4,364,271 · App. 06/149,558
Optical refractometer
Inventor:
Keith D. Froome
Patented Case
View Patent ↗
Granted: Dec 21, 1982
Filed: May 13, 1980
Inventor
Keith D. Froome
Assignee (at issue)
NATIONAL RESEARCH DEVELOPMENT CORPORATION
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.