Castaing machine

The Castaing machine is a device used to add lettering and decoration to the edge of a coin. Such lettering was necessitated by counterfeiting and edge clipping, which was a common problem resulting from the uneven and irregular hammered coinage. When Aubin Olivier introduced milled coinage to France, he also developed a method of marking the edges with lettering which would make it possible to detect if metal had been shaved from the edge. This method involved using a collar, into which the metal flowed from the pressure of the press. This technique was slower and more costly than later methods. France abandoned milled coinage in favour of hammering in 1585.

England experimented briefly with milled coinage, but it wasn't until Peter Blondeau brought his method of minting coins there in the mid-seventeenth century that such coinage began in earnest in that country. Blondeau also invented a different method of marking the edge, which was, according to him, faster and less costly than the method pioneered by Olivier. Though Blondeau's exact method was secretive, numismatists have asserted that it likely resembled the later device invented by Jean Castaing. Castaing's machine marked the edges by means of two steel rulers, which, when a coinage blank was forced between them, imprinted legends or designs on its edge. Castaing's device found favour in France, and it was eventually adopted in other nations, including Britain and the United States, but it was eventually phased out by mechanised minting techniques.

Prior to the introduction of milled coinage, hammered coinage, which resulted in a relatively crude product of irregular shape and size, predominated in European mints. In c. 1550, an Augsburg goldsmith named Max Schwab created a new technique for striking coins, which included the use of rolling mills, presses to cut the coinage blanks and the coinage press. After learning about the invention via the French ambassador, King Henry II dispatched the Comptroller of Finance Guillaume de Marillac and François Guilhem, Master of the Mint in Lyon, to observe the machinery. Schwab's press was turned with a weighted wooden handle, which exerted even pressure across the coinage blank, creating a sharper and more precise strike than hammering. De Marillac requested that Anne de Montmorency send him an engineer capable of creating a similar machine; he sent the engineer Aubin Olivier. Olivier viewed the machine, and introduced his own version to France, to which he later added a segmented collar. This allowed for the expanding metal to fill the collar, creating reeding, designs or edge lettering at the same time as the obverse and reverse images were struck onto the coin. The segments of the collar were then removed, and the coin ejected. Such lettering was used to aid in detecting coins which were debased by clipping metal from their edges, a problem frequently encountered in hammered coinage. Olivier's method of striking coins was considered costly relative to the previously utilised method, as the upper coinage die often came into contact with the collar on its downward descent, causing expensive damage. Milled coinage was thus abandoned in 1585 in favour of hammering.

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