(a) Proof of the service of the summons and complaint or of the deposit thereof in the post office, shall be as follows:
(1) If the service or deposit in the post office is by the marshal or his deputy, the certificate of such officer;
(2) If by any other person, his affidavit thereof;
(3) In case of publication, the affidavit of the publisher or his representative, together with a copy of the publication; or
(4) The written admission of the defendant.
(b) In the case of service otherwise than by publication, the certificate, affidavit, or admission must state the time and place of service; and in case of deposit in the post office, the time and place thereof.