An association may invest its funds in the bonds or interest bearing obligations of any other state of the United States upon which there is no existing default and upon which there has been no default for more than ninety days within ten years immediately preceding the investment: PROVIDED, That such state has not been in default for more than ninety days, within said ten years, in the payment of any part of the principal or interest of any debt contracted by it or for which the faith of such state was pledged.