Jean Castaing

Jean Castaing (fl. 1685–1700) was a French engineer and inventor of the Castaing machine, a device used to add edge lettering to coins. Though edge lettering had existed for over a century, the earliest methods were costly and time-consuming. In 1649, Peter Blondeau introduced a new method at the Royal Mint in England, which he kept secret. Later, in 1685, Castaing proposed that his machine be used in the mints of France. His proposal was approved, and Castaing later became general manager of all the mints in the nation.

Castaing introduced other ideas, including the reforming and recoining of already existing French coins with edge lettering to reduce instances of counterfeiting and raise money for King Louis XIV's efforts in the Nine Years' War. During the carrying out of one such operation, Castaing was accused of malversation. His wife, Marie Hippolyte Castaing (née Bosch) petitioned the court on his behalf, and he was freed two years later. He died at some point in the early eighteenth century.

Before milled coinage gained precedence in Europe, the irregular and crude hammered coinage was relatively easy to counterfeit and subject to clipping, an act which involved removing valuable metal from the edge of a coin before placing it back into circulation. In the sixteenth century, the French engineer Aubin Olivier introduced to France the coin press, to which he added a split collar capable of creating edge lettering. In order to remove the newly struck coin, the collar had to be disassembled, which was a time-consuming process. In addition, the upper coinage die was prone to strike the collar on its descent, causing expensive damage.Peter Blondeau addressed those concerns when, in 1649, he was summoned to the Royal Mint in England to modernise minting operations there. Blondeau introduced a method for edge lettering which he claimed was considerably faster and less costly than the earlier, well-known technology, but he maintained secrecy in regards to the device.

In c. 1679, Jean Castaing invented a machine capable of applying edge lettering to 20,000 coins daily. He approached the French government in 1685 in the hope of getting it adopted into use at the French mints.King Louis XIV was a proponent of the machine, but its introduction was opposed by Jean-Baptiste Colbert, Louis' financial minister, who believed edge lettering unnecessary and the machines too costly to install. In 1686, however, Castaing's proposal was approved by the Council of State, and he entered into a contract to install his machine at the various French mints.

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