Notwithstanding any other provision of law, any national banking association may, with the approval of the Comptroller of the Currency and by vote of shareholders owning a majority of the stock of such association, upon not less than five days' notice, given by registered mail or by certified mail pursuant to action taken by its board of directors, issue preferred stock of one or more classes, in such amount and with such par value as shall be approved by said Comptroller, and make such amendments to its articles of association as may be necessary for this purpose; but, in the case of any newly organized national banking association which has not yet issued common stock, the requirement of notice to and vote of shareholders shall not apply. No issue of preferred stock shall be valid until the par value of all stock so issued shall be paid in and notice thereof, duly acknowledged before a notary public by the president, vice president, or cashier of said association, has been transmitted to the Comptroller of the Currency and his certificate obtained specifying the amount of such issue of preferred stock and his approval thereof and that the amount has been duly paid in as a part of the capital of such association; which certificate shall be deemed to be conclusive evidence that such preferred stock has been duly and validly issued.