Section 660.504 - Vessel identification(a)Official number. Each fishing vessel subject to this subpart 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 visible from enforcement vessels and aircraft.(b)Numerals. The official number must be affixed to each vessel subject to this subpart in block Arabic numerals at least 14 inches (35.56 cm) in height. Markings must be legible and of a color that contrasts with the background.