## Facts

- Mason and Hepburn claimed the same invention: a one-piece firearm magazine.
- Hepburn filed a patent application in April 1894, and a patent issued to him in September 1894.
- Mason filed an application for substantially the same invention in December 1894, triggering a Patent Office interference.
- Mason asserted he conceived the invention around 1887 and reduced it to practice by having a working magazine made at a gun company.
- Mason’s device was known only to him and a small number of company employees, was not publicly disclosed or commercially exploited, and was stored for years without further action.
- The Commissioner of Patents awarded priority to Hepburn.
- Mason appealed to the Court of Appeals for the District of Columbia.

## Issues

1. Whether an earlier inventor who secretly reduced an invention to practice and then delayed seeking patent protection may establish priority in an interference over a later, independent inventor who promptly filed and obtained a patent.
2. Whether prolonged inaction and secret retention amount to suppression or concealment that forfeits an earlier inventor’s priority claim in an interference.

## Decision

- The court affirmed the Commissioner of Patents.
- The court awarded priority to Hepburn, leaving his patent in force.
- The court rejected Mason’s attempt to antedate Hepburn based on Mason’s earlier but undisclosed reduction to practice followed by extended delay.

## Legal Principles

- Priority in an interference may be denied to a first inventor who, after reduction to practice, unreasonably delays or keeps the invention secret such that the conduct constitutes abandonment, suppression, or concealment.
- Secret reduction to practice followed by long dormancy, without reasonable diligence toward patenting or making the invention publicly available, does not justify displacing a later inventor who promptly brings the invention into the patent system.
- The patent system favors timely disclosure and diligent pursuit of patent rights; an inventor who effectively withholds an invention from public knowledge for years may forfeit priority against a later, diligent applicant.

## Conclusion

The court held that Mason’s earlier but secret and long-dormant work could not defeat Hepburn’s later invention where Hepburn promptly sought and obtained patent protection, treating Mason’s delay and concealment as a bar to priority in the interference.


Mason v. Hepburn, 13 App. D.C. 86 (D.C. Cir. 1898)