(a) If more than one series of obligations is issued under this chapter payable from and secured by identical revenue, the priority of a lien against that revenue depends on the time of delivery of the obligations. A lien for a series of obligations is prior and superior to a lien for another series of obligations subsequently delivered.
(b) For an issue or series of obligations that are authorized as a unit but delivered periodically in blocks, the board may, in the proceedings authorizing the issuance of the obligations, provide that all the obligations of the issue or series are coequal as to lien regardless of the time of delivery.