Section 28. A company shall issue only such amounts of stock and bonds, coupon notes and other evidences of indebtedness payable at periods of more than one year after the date thereof, as the department may from time to time determine to be reasonably necessary for the purpose for which such issue of stock or bonds has been authorized. The department shall render a written decision upon an application for such issue within thirty days after the final hearing thereon, assigning the reasons therefor, and shall, if authorizing such issue, specify the respective amounts of stock, bonds, coupon notes or other evidences of indebtedness as aforesaid, which are authorized to be issued for the respective purposes to which the proceeds thereof are to be applied, and the decision shall, within seven days after it has been rendered, be filed in the office of the department. A certificate of the decision shall, within three days after it has been rendered and before the stock, bonds, coupon notes or other evidences of indebtedness as aforesaid are issued, be filed in the office of the state secretary, and a duplicate thereof delivered to the company. Such company shall not apply the proceeds of such stock, bonds, coupon notes or other evidences of indebtedness as aforesaid to any purpose not specified in such certificate.