(a) Whenever the advertising of a certificated repair station indicates that it is certificated, it must clearly state its certificate number.

(b) Paragraph (a) of this section applies to advertising in --

(1) Business letterheads;

(2) Billheads and statements;

(3) Customer estimates and inspection forms;

(4) Hangar or shop signs;

(5) Magazines, periodicals, or trade journals; or

(6) Any form of promotional media.