Bonds shall be numbered consecutively beginning with one, and shall be in such denominations as the council may fix by motion, and shall be secured by the assessments in the local improvement district as provided by law, and shall not be issued in excess of the cost and expense of the improvement and interest as aforesaid. Interest coupons may have printed thereon a facsimile of the signature of the officers hereinbefore authorized to execute same, and may not in fact be signed by them. Bonds may be called at the interest-paying date as provided by law. (1957 code § 8.02.090.)