Ship registries date back to the Nineteenth century on Earth till at least the 24th centuries, with Starfleet using registry codes on their starships to denote the ship's status, such as using USS to denote a standard starfleet ship, and NX to denote experimental or prototype ships. The Romulan Star Navy used several codes over the centuries: ChR and PWB were more prevalent in the 23rd century, while the prefix IRW was more prevalent in the 24th century and the RIS prefix was usually reserved to Tal Prai'ex ships. (RIS Bouteina)