Granted Patent
Utility
US 4,570,171 · App. 06/636,461
Electrochromic marking systems
Inventor:
William M. Hung
Patented Case
View Patent ↗
Granted: Feb 11, 1986
Filed: Jul 31, 1984
Inventor
William M. Hung
Assignee (at issue)
Hilton Davis Chemical 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.