Mo. Rev. Stat. § 476.030: Private seal used, when.

When no seal is provided, the clerk may use his private seal for the authentication of any record, process or proceeding required by law to be authenticated by the seal of the court; and the attestation of the clerk, stating that he has no seal of office, and that he has affixed his private seal, shall be received as sufficient authentication, without requiring any proof of such private seal, or that it was affixed.