Either the "A1" date (application published with search report) or the "A2" date (application published without search report) is the date of publication of an application in the European Patent Office for the purposes of section 15(1) of the Patents Ordinance. The "A3" date is the date of publication of the separate search report, not the application itself. The "A3" date is not relevant for the purposes of section 15(1) of the Patents Ordinance.
Is a copy of the published specification issued by the European Patent Office sufficient for the purposes of section 23(3)(a) of the Patents Ordinance?
Yes, a copy of the published specification of the designated patent is sufficient for the purposes of section 23(3)(a) of the Patents Ordinance if the person filing it confirms that it is a true copy of the document issued by or kept at the relevant designated patent office.
