A milled-edge coin has various forms of graining, ribbing, or serrulation around its circumference. In an Order of Council of May 1661 Charles II, king of England, set forth that all coin was to be struck as soon as possible by machinery, with grained or lettered edges, to stop clipping, cutting, and counterfeiting. As the order reveals, the motivation for the serrulated edges lay in the search for a means to discourage clippers, who removed bits of precious metal from the edges of coins, diminishing the metal content of coins without rendering them completely unacceptable in exchange. Hammered coins minted by hand produced coins of irregular shape that invited clipping.
Mechanized minting began in Italy, which may also have been the birthplace of the milled edge. Mechanized minting passed from Italy to France and Germany, and then to Spain and England. In 1553 Eloy Mestrell fled from Paris where he was engineer to the mint, and arrived in London, bringing knowledge of the methods of a horse-powered mill that turned out uniform blank coins, stamped with uniform images, and a milled-edge circumference. The machine for milling the edge made use of counterrotating hand screws. Mestrell’s coins that survived are of impressive quality, but he faced strong opposition from established moneyers. After an inquiry yielded adverse findings, Mistrell was relieved of his duties at the mint, and six years later he was hanged for counterfeiting.
The Paris mint again lost talent to London in 1625 when Nicholas Briot, chief engraver in Paris, left France out of frustration over the opposition of the established moneyers. Between 1631 and 1640 Briot minted silver coins with milled edges, but hammered coins still dominated English coinage. In 1649 Pierre Blondeau, an engineer from the Paris mint, arrived in London. Blondeau had developed an inexpensive and practical method of producing the milled edge, prompting Louis III of France to ban the minting of hammered coins in 1639. In England Blondeau minted a token quantity of milled-edge coins. Apparently, both Briot and Blondeau returned to France after the Commonwealth government refused to progress beyond the experimental stage with the new methods of coinage.
After the Restoration returned Charles II to the throne, he recalled Blondeau from France, and awarded him a 21-year contract to develop and apply methods for making milled and engrained edges. The contract for turning out blanks and stamping fell to three Flemish brothers, John, Joseph, and Phillip Roettier. In 1663 the Tower mint produced a one-pound coin that signaled the beginning of mechanized minting in England.
Methods for minting coins with the serrulated or corrugated edge also passed from France to Spain. In the English colonies and early United States, the Spanish milled dollar was among the most popular and widely circulated coins, passing as legal tender for brief periods. The Spanish milled dollar established the dollar as the principal unit of currency in the United States.
The practice of milled-edge coinage continues to the present day. In the United States, coins in denominations larger than a nickel have milled edges.