Mo. Rev. Stat. § 700.021
Seals may be issued by the commission when applied for with an affidavit certifying that the person applying will not attach a seal to any manufactured home or modular unit that does not meet or exceed the code. Any registered dealer who has acquired a preowned manufactured home or modular unit without a seal may apply for a seal with an affidavit certifying that the preowned manufactured home or modular unit was brought up to or otherwise meets the requirements of the code. No person may manufacture in this state any manufactured home or modular unit unless it bears a seal and certification certifying that the manufactured home or modular unit meets or exceeds the code. The certificate as to each manufactured home or modular unit shall be displayed in a manner to be prescribed by the commission.
§ 700.021, RSMo