The first steam coining press was invented by M. Thonnelier, of France, in 1833, and was first used in the United States Mint in 1836. It was remodeled and rebuilt in 1858, but in 1874 was superseded by the one now in operation, the very perfection of mechanism, in which the vibration and unsteady bearing of the former press were entirely obviated, and precision attained by the solid stroke with a saving of over seventy-five per cent. in the wearing and breaking of the dies. [Illustration: STEAM COINING PRESS.] DIES. [Illustration: DIES.] The dies for coining are prepared by engravers, especially employed at the Mint for that purpose. The process of engraving them consists in cutting the devices and legends in soft steel, those parts being depressed which, in the coin, appear in relief. This, having been finished and hardened, constitutes an “_original die_,” which, being the result of a tedious and difficult task, is deemed too precious to be directly employed in striking coins; but it is used for multiplying dies. It is first used to impress another piece of soft steel, which then presents the appearance of a coin, and is called a _hub_. This hub, being hardened, is used to impress other pieces of steel in like manner which, being like the original die, are hardened and used for striking the coins. A pair of these will, on an average, perform two weeks’ work. TRANSFER LATHE. [Illustration] The transfer lathe, a very complicated piece of machinery, is used in making dies, for coins and medals. By it, from a large cast, the design can be transferred and engraved in smaller size, in perfect proportion to the original. THE COINING AND MILLING ROOMS. This department, the most interesting to the general visitor, occupies the larger portion of the first floor on the east side of the building. The rooms are divided by an iron railing, which separates the visitors, on either side, from the machinery, etc., but allows everything to be seen. [Illustration: MILLING MACHINE.] The planchets, after being adjusted, are received here, and, in order to protect the surface of the coin, are passed through the milling-machine. The planchets are fed to this machine through an upright tube, and, as they descend from the lower aperture, they are caught upon the edge of a revolving wheel and carried about a quarter of a revolution, during which the edge is compressed and forced up—the space between the wheel and the rim being a little less than the diameter of the planchet. This apparatus moves so nimbly that five hundred and sixty half-dimes can be milled in a minute; but, for large pieces, the average is about one hundred and twenty. In this room are the milling machines, and the massive, but delicate, coining presses, ten in number. Each of these is capable of coining from eighty to one hundred pieces a minute. Only the largest are used in making coins of large denominations. [Illustration: PERFECTED COINING PRESS.] [Illustration: COINING PRESS.]