Wyo. Stat. § 34-2-126: Unsealed writings.

There shall be no difference in evidence between sealed and unsealed writings and every writing not sealed shall have the same force and effect that it would have if sealed. A writing under seal may, therefore, be changed or altogether discharged by a writing not under seal. An agreement in writing without seal for the compromise or settlement of a debt is as obligatory as if the seal were affixed.