Proof of service must be provided in a letter on company letterhead from the owner, operator, or master of the vessel on which the applicant obtained the service. The letter must contain the information described in Sec. 13.127(a). [CGD 79-116, 60 FR 17142, Apr. 4, 1995, as amended by USCG-2004-17914, 78 FR 77995, Dec. 24, 2013]