## Facts

- Coffin, as assignee, sued Ogden and others in equity to enjoin manufacture of door locks alleged to infringe a patent covering a reversible latch lock usable on right- or left-opening doors.
- The patent issued in 1861 and was reissued in 1863; Coffin acquired the patent by assignment in 1864.
- Defendants asserted invalidity based on prior invention and use by Barthol Erbe, contending the patented invention (or a substantial part) was previously known and used in the United States.
- The evidence fixed Kirkham’s invention date at March 1861.
- The evidence also established Erbe made a lock embodying the reversible latch design no later than January 1, 1861, with testimony placing his first such lock in late 1860.
- Witnesses described multiple Erbe-made locks, including examples provided to others and one sent to Washington in connection with a patent application.
- Testimony from Erbe and corroborating witnesses supported that Erbe’s lock was completed, capable of operation, and known among multiple persons in the relevant community.
- The circuit court found Erbe anticipated the patent and dismissed the bill; Coffin appealed.

## Issues

1. Whether defendants proved that Erbe invented the same or substantially the same reversible latch lock before Kirkham, defeating the patent for lack of originality/novelty.
2. What proof is required to sustain a defense of prior invention and use by someone other than the patentee in a patent infringement suit.

## Decision

- The Supreme Court affirmed the decree dismissing Coffin’s bill.
- The Court found Erbe’s invention predated Kirkham’s and anticipated the patented invention.
- The Court held defendants satisfied the demanding evidentiary showing for prior-invention invalidity by proving Erbe’s device was complete, operative, known to multiple persons, and actually used successfully.
- Because Kirkham was not the first inventor, Coffin could not enforce the asserted monopoly against defendants.

## Legal Principles

- A patent is invalid against an asserted monopoly when credible proof shows a prior inventor previously made a complete device capable of working, which was known to multiple persons and was put to successful use.
- The defense of prior invention and use is subject to strict evidentiary requirements; it is not met by unverified conception, secret prototypes, or abandoned experimentation.
- Priority turns on reduction to practice and sufficient knowledge/use such that the earlier invention qualifies as previously “known and used” before the patentee’s invention date.

## Conclusion

The Court upheld dismissal of the infringement suit because defendants proved that Erbe’s earlier, completed and successfully used reversible latch lock—known among several persons—anticipated the later patented design, rendering the patent unenforceable as to the claimed exclusive right.


Coffin v. Ogden, 85 U.S. (18 Wall.) 120 (1873)