hull classification symbol

The United States Navy uses hull classification symbols (sometimes called hull codes) to identify the types of its ships. The Royal Navy and some European and Commonwealth navies use a somewhat analogous system of Pennant numbers.The combination of symbol and hull number identify a modern Navy ship uniquely. A heavily modified or repurposed ship may receive a new symbol, and either retain the hull number or receive a new one. Also, the system of symbols has changed a number of times since it was introduced in 1907, so ships' symbols sometimes change without anything being done to the physical ship.
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