Argent le Roy Pubblico Deposited
i.e., the King's silver. When this term was used in connection with coins issued in France during the Middle Ages it implied that the metal was 23 karats fine. In a document of 1378 the Grosso of Charles V of France is called Argento le Roy, probably on account of the purity of the metal.
- Frey's Dictionary (American Journal of Numismatics, Vol. 50, 1916)