Iowa Code § 353.8: Registration — call.

All anticipatory warrants drawn under the provisions of this chapter, shall be numbered consecutively, and be registered in the office of the county treasurer and be subject to call in numerical order at any time when sufficient money derived from the sale of such limestone or the payment of a special assessment levied therefor, is in the hands of the county treasurer to retire any of said warrants together with accrued interest thereon.