For the purposes of §§ 19-5-310 and 19-5-320 any finding, report or record, or duly certified copy thereof, purporting to have been signed by such officer or employee of the United States as is described in said sections, shall prima facie be deemed to have been signed and issued by such an officer or employee pursuant to law, and the person signing the same shall prima facie be deemed to have acted within the scope of his authority. If a copy purports to have been certified by a person authorized by law to certify the same such certified copy shall be prima facie evidence of his authority so to certify.