The Carolingian penny was originally a 0.940-fine silver coin weighing pound. It was adopted by Offa of Mercia and other English kings and remained the principal currency in Europe over the next few centuries until repeated debasements necessitated the development of more valuable coins. The British penny remained a silver coin until the expense of the Napoleonic Wars prompted the use of base metals in 1797. Despite the decimalization of currencies in the United States and, later, throughout the British Commonwealth, the name remains in informal use.