It shall be the duty of the Attorney General or the district attorney of the county where the land is situate, when he shall be informed or have reason to believe that any lands in the state are being held contrary to the provisions of this act,¹ or the provisions of the Constitution of this state, to institute suit in behalf of the State of Oklahoma in the district court of the county in which said lands are situate, praying for the escheat of the same in behalf of the state, and proceed therein as in cases provided by law for escheats of lands or property where such property has no known owner: Provided, that before any such suit is instituted, the Attorney General, or district attorney aforesaid, as the case may be, shall give thirty (30) days' notice by registered letter of his intention to sue, directed to the owner of the lands, at his last-known post office address or to the persons who last rendered the same for taxes, or to any known agents of the owner; proof of having mailed such registered letter shall be deemed and held prima facie evidence of the giving of such notice.