Wyo. Stat. Ann. § 15-8-105

The bonds shall be sold for cash, or may be sold or exchanged for any other city or town indebtedness for the redemption of which they were issued, but no bonds may be sold or exchanged for less than their par value and the accrued interest at the time of disposal. No city or town indebtedness may be redeemed for more than its face value and the interest due. If part of the bonds are sold for money, the proceeds shall be applied exclusively toward the redemption of the indebtedness for which the bonds were issued. The treasurer of the city or town shall give notice of his readiness to redeem the indebtedness and that the interest on it shall cease after thirty (30) days from the date of the notice.