Proof of service must be provided in a letter on company letterhead from the owner or operator of a terminal; the owner or operator of a tank barge; the owner, operator, or master of a tank vessel; or the employer of shore-based tankermen. The letter must contain the information required by Sec. 13.127(a), excluding paragraph (a)(4)(vii). [CGD 79-116, 62 FR 25134, May 8, 1997, as amended by USCG-2004-17914, 78 FR 77996, Dec. 24, 2013]