When classification has been made of cotton inspected and sampled under supervision of a Division employee there shall be issued a cotton class certificate known as a Form C certificate. Each Form C certificate shall show the true classification of the cotton in the respects specified in the request. Such certificate, when it has been once reviewed in accordance with §28.66, shall be deemed to be a final certificate as to the classification shown, within the meaning of section 4 of the Act (42 Stat. 1517; 7 U.S.C. 54), in all cases except when superseded by a certificate or award made as provided in §28.161.