When each unpledged share of a given series, other than a full paid share reaches the value of $200, $300 or $400, all payment of dues thereon shall cease and the holder thereof shall be paid therefor out of the funds of the association, with such rate of dividend as shall be determined from time to time by the board of directors for the period of time the board shall declare such share to have matured until paid; but at no time shall more than a third of the receipts of the association be applicable to the payment of matured shares, without the consent of the board of directors. The order of payment of the matured shares shall be determined by the board of directors. Before paying matured shares all arrears and fines shall be deducted therefrom. Holders of such matured shares shall remain shareholders until the same are paid, and shall not become creditors. They may remain in the association and shall be treated in all respects as holders of full paid shares. Such matured shares may be exchanged for full paid income shares.