Every employer shall provide each employee on the termination of his employment with a certificate of service showing full names of the employer and employee, the nature of the employment, the dates of commencement and termination of the contract and the rate of remuneration at the date of such termination, and shall forward a copy of such certificate of service to the Regional Council concerned: Provided that where in this Agreement the wage of any employee is determined by length of service it shall be incumbent on the employee to produce a certificate of service to his new employer on change of employment in order to become entitled to such remuneration prescribed for length of service.