An appointee shall not act as deputy until:
(a) A written appointment by the deputy’s principal is filed with the county clerk.
(b) A copy of the appointment is filed with the county auditor, if the auditor has so requested.
(c) The deputy has taken the oath of office.
A revocation of the appointment of any deputy shall be made and filed in the same manner as the appointment.
Five years after the date of revocation of appointment of a deputy, the written oath of office subscribed to by such deputy may be destroyed and no reproduction thereof need be made or preserved.