Securities authorized to be issued under provisions hereof may be issued in an amount not exceeding 10% of the benefits confirmed and approved in accordance with Articles IV and V of the Conservancy Act [of New Mexico] and the proceeds upon the sale, exchange or delivery thereof shall be devoted to conserving and developing the resources of said conservancy district, the servicing of outstanding obligations thereof or any other expenses and carrying charges of said district, but no property which has paid in full its construction fund assessment prior to the issuance of said securities shall be subject to the conservation and development fund assessment.