The articles of incorporation of the corporation and amendments to the articles shall be submitted to the department. The approval of the articles and amendments by the commissioner of commerce and insurance, referred to as the “commissioner” in this chapter, shall be endorsed on the articles and amendments before the articles and amendments are filed with the secretary of state; provided, that if the articles of incorporation of the corporation have been filed with the secretary of state prior to April 15, 1949, the approval of the articles by the commissioner shall be evidenced by a separate instrument in writing, filed with the secretary of state.