46 CFR § 160.053-5 - Marking.
(a) Each work vest must have the following information clearly printed in waterproof lettering that can be read at a distance of 2 feet:
(b) Additional marking required. In addition to the wording included on the marking tag, on a front compartment of each work vest there shall be stenciled in waterproof ink in letters not less than one inch in height, the words, “WORK VEST ONLY.”
(c) Waterproofness of marking tags. Marking tags shall be sufficiently waterproof so that after 48 hours submergence in water, they will withstand rubbing by hand with moderate pressure while wet without the printed matter becoming illegible.