Notwithstanding Article 5(6), a Member State may, if circumstances require, allow a seafarer to serve in a capacity other than radio officer or radio operator, except as provided by the Radio Regulations, for a period not exceeding three months on board a ship flying its flag, while holding an appropriate and valid certificate issued and endorsed as required by a third country, but not yet endorsed for recognition by the Member State concerned so as to render it appropriate for service on board a ship flying its flag.