Granted Patent
Utility
US 4,558,540 · App. 06/461,994
Knife sharpener
Inventor:
Walter W. Collins
Patented Case
View Patent ↗
Granted: Dec 17, 1985
Filed: Jan 28, 1983
Inventor
Walter W. Collins
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.