The owner or owners of any unpatented mining claim heretofore located may waive and relinquish all rights thereunder which are contrary to or in conflict with the limitations or restrictions specified in section 612 of this title as to hereafter located unpatented mining claims. The execution and acknowledgment of such a waiver and relinquishment by such owner or owners and the recordation thereof in the office where the notice or certificate of location of such mining claim is of record shall render such mining claim thereafter and prior to issuance of patent subject to the limitations and restrictions in section 612 of this title in all respects as if said mining claim had been located after July 23, 1955, but no such waiver or relinquishment shall be deemed in any manner to constitute any concession as to the date of priority of rights under said mining claim or as to the validity thereof.