49 CFR § 172.303 - Prohibited marking.
(a) No person may offer for transportation or transport a package which is marked with the proper shipping name, the identification number of a hazardous material or any other markings indicating that the material is hazardous (e.g., RQ, INHALATION HAZARD) unless the package contains the identified hazardous material or its residue.
(b) This section does not apply to—
(2) Markings on a package which are securely covered in transportation.
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