50 CFR 300.125 - Vessel identification.
(a)Official number. A vessel with a permit issued pursuant to § 300.123, when in treaty waters, must display its official number on the port and starboard sides of the deckhouse or hull, and on an appropriate weather deck, so as to be clearly visible from an enforcement vessel or aircraft. The official number must be permanently affixed to or painted on the vessel and must be in block arabic numerals in contrasting color to the background at least 18 inches (45.7 cm) in height for fishing vessels over 65 ft (19.8 m) in length, and at least 10 inches (25.4 cm) in height for all other vessel.
(1) Keep the official number clearly legible and in good repair.