A change of beneficiary of an adjusted service certificate to be valid must be made:
(b) Or by last will and testament of the veteran, duly probated. Such change shall not be effective until received by the Department of Veterans Affairs and approved by the Secretary and after such approval the change shall be deemed to have been made as of the date of death of the veteran: Provided, That a change of beneficiary signed subsequent to the date upon which the will was executed and delivered in accordance with paragraph (a) of this section shall if approved in accordance with regulations take precedence over the designation by will. Provided, however, That any payment made to a beneficiary of record, before notice of change of beneficiary has been received in the Department of Veterans Affairs and approved by the Secretary, shall not be made again to the changed beneficiary.