Special purpose revenue bonds shall be payable solely from the revenues derived by the department from payments made to the department under the project agreement or other agreements entered into with respect to the project, and shall be secured solely by such revenues and by the pledges and assignments authorized by this part. All special purpose revenue bonds of the same issue, subject to the prior and superior rights of outstanding bonds, claims, obligations, or mechanics’ and materialmen’s liens, shall have a prior and paramount lien on the revenues derived from the project agreement with respect to the project, for which such bonds have been issued, over and ahead of all special purpose revenue bonds of any issue payable from the revenues which may be subsequently issued and over and ahead of any claims or obligations of any nature against the revenues subsequently arising or subsequently incurred; provided that the department may reserve the right and privilege to subsequently issue additional series of special purpose revenue bonds, from time to time, payable from the revenues derived from such project agreement on a parity with the special purpose revenue bonds theretofore issued, and the subsequently issued series of special purpose revenue bonds may be secured, without priority by reason of date of sale, date of execution, or date of delivery, by a lien on the revenues in accordance with law, including this part.