1. MANUFACTURING OF COINS by, SARAVANAN S 0205-PGTE

2. Coin Diagram with Terms and Definitions

3. DEFINITIONS Device - a design element on the coin such as a bust of a person, and eagle or any other element. Usually the devices are raised, but on some coins they are below the coin surface (incused). Rim - A rim is where the edge and the obverse and reverse sides of the coin meet. On many coins there is a raised rim as shown above. The rim can be seen on both the reverse and obverse on this coin. The rim is used to help protect the coin from wear, by providing a raised surface right around the circumference of the coin.

4. Edge - The edge of the coin is called the "third side" by some. The edge can be plain (smooth), reeded, ornamented, or have letters embossed into it. The edge is the side around the circumference of the coin, the edge is not the same as the rim, the coin rolls on its edge.

5. Obverse - The face or front of a coin. "Heads." Usually has a person, date on this side, but not always Reverse - The back of the coin. "Tails." Usually has secondary design elements, the denomination, and other inscriptions. But not always (look at some modern commems). Fields - The open areas of the design, usually they serve as the background and surround the devices. Clean fields are desired in rare coins. Fields that do not have bag marks and are mirror smooth can raise the grade of a coin. Denomination - The monetary value of the coin Mint mark - the mint that produced the coin usually stamps a mint mark for the coin. This shows what mint struck the coin. Most common in the U.S. are S, P, D, CC, O, and WW. mint mark

6. Legend - The words on a coin are the legend or inscription. Motto - an inscription that has special meaning in the country, such as "In God We Trust" -- the motto of the U.S. Exergue - The area set off from the design for the date. Many times this can be delineated with a line or depressed area. (See the buffalo nickel.) Dentils (aka Denticles) - the small serrated edge around the rim (tooth- like design around the circumference of the rim). Sometimes small dots can be used, but often, just a gear-like design

8. Coin Dies Reverse and obverse coin dies for the spectacular 100 Escudo gold piece, the largest Spanish coin ever struck at 76mm in diameter and over 11 ounces in weight, an exclusive issue produced only at the Royal Mill Mint of Segovia. Click on picture for full size photo

9. COMPOSITION OF US COINS standard alloy of 95 % Cu and 5 % Zn ie., copper-plated zinc. Homogeneous alloy 75 %copper and 25 % nickel (five-cent coin ) "clad" coins (ten-cent coin, quarter-dollar coin, half-dollar coin and one-dollar coin) produced from three coin strips that are bonded together and rolled to the required thickness.

10. MANUFACTURING Coin strip is fed into high-speed automatic presses which cut the coin blanks, known as planchets The cupronickel planchets are softened by annealing in a special furnace then they are chemically cleaned in large rotating barrels & dried

11. Next, the planchets are put through an edge-rolling operation in the upsetting machine - edge hardens during this process - It also removes any burrs Finally, the upset planchets are stamped with the designs and inscriptions to make coins

12. Generally, the manufacturing process is the same for all denominations The difference is the marking with tiny ridges -"reeding”(a safety measure) After striking, each coin is inspected The coins are then counted and bagged Each bag is weighed before shipment to ensure that it contains the correct number of coins.

13. SOUTH AFRICAN MINT ANNEALING During the annealing process the coin blanks are softened by heat treatment in preparation for minting. All coin blanks are polished after heat treatment to give them a high quality surface finish and special anti tarnishing chemicals are added to the polishing process.

14. BLANKING Blank circular discs are punched out of metal strip. Each of the four high-speed blanking presses can produce 4000 coin blanks per minute. (At this stage unique edge marking is applied to coins if required by the client). Each coin blank is rimmed before it is kept in the blank store for the next process.

15. COINING The prepared coin blanks are coined on one of thirteen high-speed presses, each producing 750 coins per minute. Finished coins are continuously subjected to rigorous quality control inspections. Coins in traditional alloys, electroplated coins and bicolour coins are minted in this department

16. CAST-COINING The Chinese minted coins by pouring molten metal into molds - known as casting - from before the Christian era up until the latter part of the ninteenth century. The molds and cast coins shown above are from Morocco, from the mid- nineteenth century

17. SOUTH AFRICAN MINT The first step in the creation of a master die is 3D modelling of the design in plasticine, followed by refinement in fine plaster. An acrylic model of the completed artwork is reduced and cut in steel by precision 3D reducing machines. The South African Mint also uses computer controlled engraving machines for high volume production items. Cut steel dies are turned into master dies from which the production dies are reproduced.

18. ELCTROPLATED COINS The manufacturing of bi-coloured coins by means of the electroplating process is one of its more recent coin product developments. Material Handling Devices Material Handling Devices (MHDs) include stores, cranes, Automated Guided Vehicles (AGVs), conveyors, drop- sections and automotors

19. Rolling Mill Coils are rolled on modern computer controlled rolling mills to produce strip of the correct thickness. Electronic measuring equipment controls the rolling gap and produces a product that is within eleven microns of the required thickness. These tolerances are essential in determining the final mass of the product

20. Hammer-struck coining The hammer-struck method was used for minting coins ever since they were first invented around the year 700 B.C. in Turkey, up until the latter part of the nineteenth century in some countries such as India

21. Hammer-struck coins had very irregular edges which inspired the illicit art of clipping bits of gold and silver from them before returning them one by one to circulation. The roller-mills, as used in Segovia, produced coins with almost perfect edges, thwarting unscrupulous individuals from performing their illicit practice

22. Roller-mill coining The coin rolling-mill was first conceived by Leonardo da Vinci and became popular in Europe around the mid- sixteenth century. This was the type of machine employed in the Segovia Mint to "roll" (not "strike") coins from 1586 through 1772 when screw- presses were finally installed. The rolling-mills (with smooth instead of engraved roller surfaces) continued to be used in Segovia however to prepare the metal strips, and are similar to machines used in mints today for the same purpose

23. JAPAN MINT PROCESS Silver plates are mechanically impressed with the design of the master die. (IMPRESSING) Unneeded portions are trimmed with a fret saw. (TRIMMING)

24. The blank is finished by filing. (FILING) The impressed blank is glazed with cloisonne enamels. (GLAZING)

25. MELTING Coinage materials are melted in an electric furnace, and ingots are produced by a continuous casting machine

26. HOT & COLD ROLLING Ingots are heated in a soaking pit. While hot they are rolled out and made into coil shape. This is followed by rough and finish rolling to complete the rolled plates having the thickness of the coins to be produced.

27. BLANKING Blank discs are punched from the finished plates. These are what we call "Engyo" (blanks).

28. EDGING To sharpen the images of coins, the peripheries of the blanks are edged. This is followed by annealing to soften the blanks

29. COINING By means of a coining press fitted with a coinage die, finished blanks are stamped with obverse (head) and reverse (tail) patterns and milled at the same time if milling is required.

30. INSPECTION The patterns of each stamped coin are inspected, and imperfect products are taken out. Accepted coins are strictly counted and then bagged.

31. EDM-CNC Coining dies can be made in cad-cam for cost savings in the simpler designs, for the better, portrait-like designs the best way is to sculpt a clay model at nine inches in diameter and cast it in epoxy resin. Then we use the finest machine available to reduce the size and cut the die into steel. (the same reducing machine that the U.S. Mint uses). We have two automatic Janvier die sinking machines with high speed precision spindles used for this. The die can then be shot with glass bead (if a frosted look is desired) and polished to near proof quality. The sculptors we have available are among the best. We can create a sculpture from artwork, or this can be supplied.

34. Screw-press This screw-press was made in the Seville Mint in 1735 and installed in the Segovia Mint to strike a new series of copper coins which began in 1772. After this date the roller-mills were only used to prepare the metal strips from which the blanks were cut, and not to roll the coin designs onto the strips as before. This press is presently on display in the Alcazar castle of Segovia