According to Rule 25 of the European Patent Convention (EPC) Implementing Regulations (IR),
Within four months of filing the European patent application, the applicant shall file the certificate that the applicant or his legal predecessor has displayed the invention at an official, or officially recognised, international exhibition ( falling within the terms of the Convention on international exhibitions signed at Paris on 22 November 1928 and last revised on 30 November 1972), which:
(a)