§ 121-a. Proof of dependency in foreign countries. In cases involving the dependency of aliens residing in foreign countries, transcripts of birth or marriage certificates, also documents and affidavits, certified by a local official or local magistrate and authenticated as to such official or magistrate by the secretary of state or other official having charge of foreign affairs, or a United States consul, in said foreign country, may be received in evidence, but in all such cases proof of present existence and of dependency may be made by the personal appearance of each and all persons claiming relationship to or dependence upon a deceased worker under the provisions of sections sixteen and seventeen of this chapter, before a diplomatic or consular officer of the United States, and statements made to or evidence presented before such diplomatic or consular officer under oath may be received in evidence in whole or in part by the board upon any such claim. Questions regarding admissibility and adequacy of evidence arising in connection with proceedings before the consul shall be determined by the board. The board may by rule prescribe the conditions under which proofs other than personal appearance before a diplomatic or consular officer of the United States may be accepted as proof of the facts of existence, relationship and dependency.