Section 204 is a somewhat broadened and liberalized counterpart of sections 28 and 29 of the present statute [sections 28 and 29 of former title 17]. Under subsection (a), a transfer of copyright ownership (other than one brought about by operation of law) is valid only if there exists an instrument of conveyance, or alternatively a “note or memorandum of the transfer,” which is in writing and signed by the copyright owner “or such owner’s duly authorized agent.” Subsection (b) makes clear that a notarial or consular acknowledgment is not essential to the validity of any transfer, whether executed in the United States or abroad. However, the subsection would liberalize the conditions under which certificates of acknowledgment of documents executed abroad are to be accorded prima facie weight, and would give the same weight to domestic acknowledgments under appropriate circumstances.