No person may operate a vessel except a vessel exempted in Sec. 173.13 that has a number issued by the Coast Guard unless it has the validation sticker issued with the certificate of number displayed within 6 inches of the number. [CGD 72-54R, 37 FR 21399, Oct. 7, 1972, as amended by USCG-2003-14963, 77 FR 18700, Mar. 28, 2012]