https://www.hakaimagazine.com/videos-visuals/the-secret-language-of-ships/
Quote:
Most ships have clues to their identity emblazoned on their stern, often in the same order: owner, name, port (or "flag"), and International Maritime Organization (IMO) number. American President Lines (APL) owns this ship, christened the Mexico City, and it sails under the flag of Singapore.
The owner, name, and flag may change over a ship's lifespan, but the IMO number stays the same as mandated by an international maritime treaty. Like vehicle identification numbers, IMOs help thwart fraud. Do a web search on an IMO number and the ship's full history pops up.
Curious about those yellow-green, fortune-cookie-shaped objects along the lines? They're anti-rat devices, foiling rodent attempts to scrabble from dock to line to ship.