## Facts

- Bo Thuresson af Ekenstam sought a U.S. patent on a method of oxidizing cyclic compounds, filing in the United States on June 2, 1951 and claiming priority to a Swedish filing date of June 12, 1950.
- The Patent Office rejected certain claims as anticipated by a single reference: a Du Pont Belgian patent (Belgian Patent No. 494,439) describing the same invention.
- The Belgian patent system used two relevant dates:
  - A “brevet octroyé” date (March 31, 1950), reflecting a formal grant following a decree, but without public access to the specification and claims.
  - A “brevet publié” date (July 1, 1950), when the application papers became publicly available.
- The Board of Appeals affirmed the examiner in a divided decision, treating the “brevet octroyé” date as the operative date and applying a statutory bar under 35 U.S.C. § 102(b).
- The dispute on appeal turned solely on which Belgian date controls the reference’s effective prior-art date for § 102(b) purposes.

## Issues

1. For purposes of 35 U.S.C. § 102(b), does a foreign patent become prior art as of the date it is formally granted when the disclosure is not public, or as of the date its contents first become publicly accessible?
2. Under Belgian practice, should the Du Pont patent’s effective date as a § 102(b) reference be the “brevet octroyé” date or the later “brevet publié” date?

## Decision

- The court reversed the Board of Appeals.
- The effective prior-art date of the Du Pont Belgian patent for § 102(b) purposes was July 1, 1950, the “brevet publié” date when the disclosure became publicly available.
- Because Ekenstam’s Swedish filing date (June 12, 1950) preceded July 1, 1950, the Belgian patent did not bar the claims under § 102(b).
- The court rejected the view that a nonpublic, “secret” grant date suffices to make a foreign “patent” available as a § 102(b) reference.

## Legal Principles

- A foreign document labeled a “patent” is prior art under § 102(a) or (b) only from the date it is publicly accessible in a meaningful way.
- A formally granted but nonpublic (“secret”) foreign patent does not qualify as prior art until the disclosure is opened to public inspection.
- For foreign patents with separate grant and publication events, the operative prior-art date is the date the specification and claims become available to the public, not the earlier administrative grant date.

## Conclusion

The court held that a foreign patent’s prior-art effect under § 102(b) depends on public accessibility of its disclosure; the Du Pont Belgian patent became effective prior art only on its publication date, so it did not bar Ekenstam’s application because his priority date preceded that public release.


Application of Ekenstam, 256 F.2d 321 (C.C.P.A. 1958)