In any case where general obligation bonds of a county or a municipality have heretofore been or may hereafter be authorized at an election held pursuant to the provisions of Article 2 or 3 of this chapter, as amended, and are issued and sold in series rather than as an entirety, it shall not be necessary for each series of such bonds to mature or be payable in the manner required by the applicable provisions of Section 11-81-6, as amended, so long as all such bonds so authorized taken together mature or are payable in the manner provided by the applicable provisions of said Section 11-81-6.

Without in any way limiting the generality of the foregoing, it is hereby declared that in cases where any such bonds are so authorized at an election and are issued and sold in series and not as an entirety, it shall not be necessary for the bonds of each such series to be payable in annual installments or for the first installment of principal of the bonds of any such series to be payable not later than three years after the date of the bonds of such series, and the largest installment of principal coming due in any successive 12-month period on the bonds of any such series may be more than two times as great as the smallest installment of principal coming due in any prior successive 12-month period on the bonds of such series.