Without prejudice to the jurisdiction of the European Patent Office under the Convention on the grant of European patents, signed at Munich on 5th October 1973, the courts of each Contracting State shall have exclusive jurisdiction, regardless of domicile, in proceedings concerned with the registration or validity of any European patent granted for that State which is not a Community patent by virtue of the provisions of Article 86 of the Convention for the European patent for the common market, signed at Luxembourg on 15th December 1975.