Section 33A. The clerk or registrar shall not issue a certificate under section 28 before receiving proof of age of the parties and verifying that both parties are not less than 18 years of age. Such proof shall be contained in any of the following documents, graded and taking precedence in the following order: (i) an original or certified copy of a record of birth; (ii) an original or certified copy of a baptismal record; (iii) a passport; (iv) a life insurance policy; (v) an employment certificate; (vi) a school record; (vii) an immigration record; (viii) a naturalization record; or (ix) a court record. The clerk or registrar shall not accept documentary evidence of a lower grade unless the clerk or registrar is satisfied that evidence of a higher grade is not readily procurable.