Milled coinage

In numismatics, the term milled coinage (also known as machine-struck coinage) is used to describe coins which are produced by some form of machine, rather than by manually hammering coin blanks between two dies (hammered coinage) or casting coins from dies.

Introduction

Until 1550, coinage techniques used in European mints had not progressed from the

clipped, i.e. precious metal was shaved from the edges of the coins. In accordance with Gresham's law, the clipped and forged coins drove good coins out of circulation, depreciating the currency.^[1]

Leonardo da Vinci's notebooks showed there was a better way^[2] and Donato Bramante, the architect who made the initial plans for St. Peter's Basilica, developed a screw press to make the lead bullae attached to Papal documents.^[3] In 1550, the French ambassador to Augsburg, Charles de Marillac, saw a way for France to get an economic advantage over the Holy Roman Empire when he learned that a local engineer had perfected a mechanical process of rolling bullion to the required thickness, cutting blanks from the rolled metal, and striking coins from those blanks. This technology was significantly more advanced than the general manufacturing processes of the 16th century^[4] making the coins difficult to counterfeit. The negotiations which obtained rights to the process for France were so secret that the inventor was identified with a codename, but he was most likely Marx Schwab. Aubin Olivier went to Augsburg to learn the technique and Henry II of France made him chief engineer of a mechanized mint in Paris, called the Moulin des Étuves, on 27 March 1551. This mint produced well-struck and perfectly round gold and silver coins. Having perfectly round coins made it easy to detect clipping, but the coiners' establishment would have none of this and within a decade the Moulin des Étuves' ex-employees were finding work in Navarre and England.^[5]

In England, a 1560 proclamation of

DECVS ET TVTAMEN, meaning an ornament and a safeguard—refers to the protection against clipping which the lettered edge provided.^[8] In accordance with Gresham's law, however, the inferior hammered coins limited the circulation of his coins until the hammered coins were demonetized in 1695.^[9]

Closeup of a working reconstruction of a 1571 roller mill in an Austrian museum in Hall

Meanwhile, in continental Europe, France readopted machine made coins in 1639. Both machine-made and hammered coins continued through the recoinage of French silver in 1641, but by now machine-made coinage's time had come, and hammered French coinage ended in 1645.

National Archaeological Museum of Spain, Madrid

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Coins of the Industrial Revolution

The Industrial Revolution shifted the focus of the economy from a rural to an urban, money based, enterprise.^[12] The main technology of the Industrial Revolution, the Watt steam engine, also increased the overall level of economic activity.^[13] Both of these factors increased the demand for money. Factories were financed by introducing paper money and credit, but low-denomination coins were required to pay their workers and in England copper coins were scarce.^[14] Matthew Boulton had backed Watt's development of the steam engine, and he used it to power coin-making machinery at his Soho Manufactory.^[15] Boulton struck coins for the East India Company, supplied steam powered coining machinery to the Moscow mint,^[16] and manufactured private tokens which circulated widely in England.^[14] In 1797, Boulton received a contract to strike royal British copper coins called cartwheels. In 1805, he received a further contract to supply steam powered coinage machinery when the British Royal Mint left the Tower of London and established a new facility on Little Tower Hill.^[16]

In the Americas and East Asia

When Spain introduced coinage to America in 1536, coins were still hammered. The fineness of the silver in this coinage was reduced in 1732 and the Mexico City mint began striking the new coins using machinery.

Spanish Milled Dollars.^[18]

The Spanish Milled Dollar, and its successor the Mexican Peso, were widely used in trade with the

shogunate was overthrown, the restored Emperor Meiji built a mint at Osaka and imported minting machinery from Birmingham, England for it.^[20] Likewise, Spanish Milled Dollars and Mexican pesos became the primary currency used for trade in large parts of southern China during the mid 1800s. China struck similar coins for Turkestan in 1877, and for its own use in 1890.^[21]

In modern practice in the United States, milling, or a milled edge, can refer to the raised edge on the coin face, applied by a special milling machine after the planchets are cut out and polished. In addition, the reeding of coins of higher value, applied by the collar holding the coin when it is stamped, can be considered part of the milled edge.^[22]^[23]