Definition

• Composition.  (2) The material from which a coin or medal is made; the metal, alloy or nonmetallic material which is fashioned into a numismatic or medallic object; its media. Factors of availability, cost, color, machinability and appearance determine which composition is most suitable for any coin or medal. In the 20th century new characteristics have appeared. For example: is it suitable for vending machines? Does it have to be in precious metal? Will it be struck or cast? If a metal, how is its coinability? Will it be left in coin finish, or given a patina finish? Will it be confused with coins of another country?
  It is interesting that the metals used from the beginning of ancient coins are still
  those same metals most popular for coins and medals today:  gold, silver and bronze. It is not that the ancients had some great insight, but rather they had the experience. These metals had been worked by man for centuries as early as 4000 bc for bronze. China’s choice for early coins was bronze, India was silver, western countries preferred precious metals silver and gold. These metals, well known and used for the earliest coins, possessed the most desirable characteristics required for coin making. They also possessed desirable wearing qualities for circulating, then as now.
   
  Metals In A Coinage System
  A coinage system that employs two metals, as gold and silver, is called a binary system. The Lydians, who first struck coins in 640 BC, developed such a two-metal binary system in 550 BC.  When a system has three metals, as gold, silver and bronze – or any three metals – for its coins is said to be on a ternary system. If four metals are employed it is a quaternary system.
  In 1920 Great Britain eliminated precious metals from their coins, going off the sterling standard, and went from a ternary to a quaternary system. A coinage alloy of three or four metal elements in one composition is also called these terms.  See alloy. (Clad compositions, which became popular in the late 20th century, have obscured these "-nary" designations; future metallurgical grammarians will be required to redefine these terms.)
  Coinage Metal Alloys
  The earliest coin makers learned that pure metal, particularly gold and silver, was too soft to withstand the harsh conditions of circulating. These metals, as with most coinage metals, were alloyed. The popularity of sterling, for example, is a silver content of .925, which required an addition of .075 copper for strength and hardness. This alloy proved satisfactory as a coinage composition, to strike, to circulate, to retain its color and its value. Later coin silver was introduced with a greater alloy of 90% silver,
  10% copper.
  Coins were struck in these alloys through the years, except for occasions when the precious metal content was reduced for political reasons: creating debased compositions. In the 19th century copper nickel was introduced and a few experiments were made in other minor coinage metals.
  Modern Alloy Problems
  The gradual rise of primary metal costs in the 20th century has brought economic pressure to change coin compositions. As mentioned, Great Britain stopped using silver in coins in 1946. The United States stopped striking silver in circulating coins in 1964 (except for silver coins sold to collectors). These changes were brought about by the increase in the market price of silver. Coins struck in alloys without precious metal became a token coinage.
  In 1965 silver coins (of 90% silver) were worth more for their silver content than
  their face value. The obvious happened: coins were withdrawn from circulation and melted. Gresham's law came into effect: coins with least intrinsic value replace in circulation coins of greater intrinsic value, "bad money drives out good money." This caused a sever coin shortage and widespread trouble for all small commercial transactions. Other countries confronted similar problems, the problem was worldwide.
  U.S. Treasury officials were faced with some difficult decisions. What also influenced the solution were the millions of vending machines and fare boxes that were engineered to accept silver coins (including tests of surface resistivity). What had to be created was a lower cost alloy that could still be accepted in all those venting machines. The solution was to strike coins in a clad composition. With a layer of silver, or silver-like metal, on each side of a lower-cost base metal, the total costs of blanks would be less, but this would still meet the requirements of the vending machine industry.
  In 1981 a similar situation occurred with the price of copper, effecting the striking of cent coins. Here again the solution was a clad composition of copper coating a zinc base metal. In the United States, cents struck from 1982 forward were of copper clad zinc composition.
  (The clad technology also created a new industry – manufacturing the clad strip and supplying this, or blanks cut from the strips, to the mints. It was also a brilliant solution for what could be done with all the skeleton scrap after the blanks were cut out. Copper coated zinc scrap, for example, could be melted, and with little reformulation – addition of virgin copper – poured into ingots of ... bronze! Scrap technology must be taken into consideration with every decision of coinage composition, see below.)
  In each of these solutions the color and appearance of the prior metal was retained (as well as surface resistivity – necessary for vending machine detectors). It is interesting to speculate what the next major change in coin compositions will require and when this will occur.
  Space Metals
  Perhaps the source for new coinage metals will come from outer space. Alloying
  metals on earth has some stringent limitations. Gold, as heavy as it is, for example, cannot be alloyed with light-weight metal, as aluminum. In space, this might be a simple task. Thus an entire new storehouse of metals is expected to be created outside earth-bound gravity restrictions. These new metals will have characteristics, perhaps, beyond our wildest expectations. Their costs will be extremely high in the beginning and will require entirely new metallurgical technologies.
  (Under the entry on medallic objects the author speculates that the organization which issues a medal in the first space metal will reap a fortune. We are looking forward with enthusiasm to the first coins and medals fabricated from space age compositions.)
  Scrap Technology
  Planning any new composition for coins needs to take into consideration how best to convert the composition into reusable metals when the coins are no longer suitable for circulation and for reprocessing the skeleton scrap. Without planning their scrap technology, early American silver coins were melted for the excellent alloy of their silver composition. Jewelers and silversmiths did not need to stock any silver, they needed only to melt silver coins to fashion into new products.
  The first concerns for new coinage alloys occurred in 1856 in America when
  copper, then used for large cents, became more costly than the face value of copper coins. Experiments were made with a copper nickel for a smaller diameter cent coin, only to select a bronze composition of 95% copper with 5% tin and zinc for alloy. At this time a
  New York dentist, Dr. Lewis Feuchtwanger, proposed a coinage alloy that included four and five different metals.
              This would have been a scrap technology nightmare had his proposal been adopted and coins struck in this composition. Actually Feuchawanger’s composition contained 60% copper, 20% nickel, and 20% zinc. The Mint did not want to use his invention, but later “thought of it themselves” only changed the alloy a bit. They used his original ideas of a smaller, thinner size cent with an eagle design on the obverse. The first U.S. small size cents, made for circulation in 1857-1864 contained an alloy of .880 copper and.120 nickel.
  The concern of scraping coins for their metal content did not become a major concern until the early 1960s, and greatly became a concern when coins were struck in CLAD composition. The great silver coin meltdown, beginning in 1964 when U.S. silver coins were withdrawn, dramatically proved to Treasury officials they must take into consideration the scraping of coins for any coin composition they considered.
  The choice of a pure copper core with silver clad on both sides was a brilliant solution. This composition can be easily melted and with addition of pure silver can be reformulated into a reusable silver alloy.
  Nonmetallic Compositions
  For centuries mint officials have wrestled with the problems of composition of the coins they were required to strike. Metal shortages, fluctuating prices, new technology, wartime metal needs, economic and political factors have all influenced coinage metal needs. Mints have experimented with substitute compositions endlessly.
  In 1868, for example, a Boston firm patented a composition it called Diatite. Unheard of today, it was one of the many unsuccessful coinage compositions, with only two tokens in existence as evidence of this experiment. In 1942 the U.S. Treasury considered producing cent coins in plastic. In other times the media listed in the adjacent chart under nonmetallic compositions have been considered to replace metal alloys for coins.
  But where most nonmetallic compositions are found is in tokens, and to a smaller degree, in medals. Tokens have been struck or fabricated in most all of the 17 materials listed in the chart. Medals, likewise have been made in more than half of these. The experience found among nonmetallic compositions for tokens and medals have given experience to mint officials not to use these compositions for coins. They still wisely use metal for coin compositions.
                  Coin And Medal Compositions              
   A. Metallic                  
       1. acmonital                                         
       2. albata                    
       3. alpacca                    
       4. aluminum                  
       5. aluminum bronze           
       6. argentin                  
       7. bath metal                
       8. brass                     
       9. bronze                                            
     10. copper                                            
     11. copper nickel (cupro-nickel)                                    
     12. Chrom-steel            
     13. Electrum                  
     14. german-silver             
     15. gold                       
     16. goldene                   
     17. iron (ferrous)            
     18. lead                    
     19. Manganese                 
     20. nickel                    
     21. nickel-brass              
     22. nickel-silver            
     23. oroide                   
     24. Orichalcum               
     25. Palladium                    
     26. pewter                   
     27.  platinum                 
     28. silver                   
     29. space metals               
     30. sterling                 
     31. tin                                               
     32. Titanium                                          
     33. tombac                 
     34. type metal             
     35. white metal                                        
     36. zinc  
                                             
  B. Plated Metals          
     1. bronze gilt        
     2. gilding metal       
     3. goldplated           
     4. rolled gold         
     5. sheffield plate     
     6. silverplated 
     7. vermeil   
           
  C. Nonmetallic            
     1. Bakelite            
     2. boxwood             
     3. ceramic              
     4. glass               
     5. hard rubber         
     6. Horn                
     7. ivory               
     8. Lava
     9  Leather   
   10. plastics            
   11. porcelain           
   12. Soap                
   13. Steatite  (soapstone)                   
   14. stone   
   15. Terra-cotta         
   16. Vulcanite           
   17. wax                 
   18. wood (bois durci)   
  Note: Terms in small caps have entries in this book.
   
  Computer Engraving.   Creating an image in varying depths digitally on a computer which establishes the controls for the milling of these depths in a die or hub. While computer engraving is a new tool in the hands of the coin and medal engraver the computer will not design a coin or medal. But like a burin in the hand of the engraver, it will aid the engraver to enter the design in MODULATED RELIEF by determining the amount of depth each point should cut into the die or matrix.
              Mints and medalmakers around the world were eager to accept the new technology, the most recent step in replacing the tedious act of hand engraving dies, as old as coins themselves. The advantages of computer engraving is not only “fast and cheap” but also its versatility to alter a design, to modify it, to test a new concept, to hone the relief to a satisfactory image. As such it is ideal for quickly developing a design in contrast to previous “clay and plaster” technology.
  Computer engraving language. Like any specialized methodology,
  engraving by computers has its own terminology. While sculptors create three dimensional relief design by carving and modeling computer engravers design with X, Y, and Z coordinates. The term for computer relief, as well as this class of engraved dies, is called 3D for the rise and fall of the modulated design. New terms describe old methods. What the hand engraver or modeler called PROVING the computer artist calls digital elevation model (DEM). Here are the most used digital terms.
   
  Word List #
   
      Computer Engraving Terms
   
  2D – Two dimension, FLAT ENGRAING
  2.5D – Two and a half dimensions, flat design on 3
  or more planes
  3D --  Three dimensional, free-form sculpture
  surface MODULATED RELIEF.
  CAD – Computer Aided Design
  CAD-CAM – Computer Aided Design plus
  Computer Aided Manufacturing.
  VS – Virtual Sculpturing
  VS3D –Virtual Sculpturing in three dimensional
  free-form modulated relief
  CNC—Computer Numeric Control
  G-Code – Standard numerical language
  DEM – Digital Elevation Model, an image with
  considerable formation of the design.
  RP – Rapid Phototyping, a method of quickly
  viewing a scale model.
  TIF – Tagged Image File, a formal digital image.
  X, Y, Z Coordinates – a design’s height (X), width
  (Y), and depth (Z) in a die, hub or matrix.
  pixel – aa individual dot in a computer image.
  tool path –track of a tool controlled by computer
  instructions
  bitmap –- a digital image composed of a marix of
  dots.
  visual feedback – appearance of the design viewed
  by a human, virtual reality.
  hammer blow  – movement of the Z coordinate in
  forming a design.
  touch-probe digitizer –a tool to alter one or more
  coordinates in a design.
  Computer engraving technique.  The computer engraver starts with a scan of a flat drawing, a cartoon, or creates this on the screen. At each point on the two-dimensional design, called a pixel, X and Y coordinates are determined by the computer. The operator chooses the depth at this point, the Z coordinate. This fixes the sculptural or dimensional effect, the depth of the relief – to form the height in the die – the depth of the Z coordinate. An individual move to lower this point is called a “hammer blow,” All three coordinates for that point are stored in the software, forming a bitmap.
  A visual image is shown on the screen of the CPR at all times. The operator moves through the design creating the modulated relief using a special tool, a touch-probe digitizer. A rapid phototype (RP) image can be obtained at any time.
  The finished and approved design fixed in the software will then be transferred to a milling machine which does the cutting as controlled by the digital file. Afterwards, burrs and rough corners from the milling tool must be worked as with any other touchup of dies.                           
  Status. Not all sculptor modellers have embraced the new computer engraving technology. Perhaps like the reaction of hand engravers to machine engravers when these were introduced in previous years, it took time to prove a new technology. Critics of computer engraving cite three shortcomings: micro modelling by the computer, portrait r    ealism, and crispness of detail. Modellers in clay or wax can apply larger areas of a design at one time, while computer modelling is limited to a single point.
  Critics say computer generated portraits are stiff, frozen and lifeless. They would still prefer working in clay or wax to vivify a portrait making it more realistic and lifelike. In art vivify means “give life to.”  Since most viewers prefer highly detailed designs with sharp edge relief, this can be obtained in both old and new methods, However It requires repeated cutting a second or third time with finer cutting points in the milling operation, somewhat more difficult with the new method. 
  Both technologies, however, have their place in the field and will continue to be employed in the minting industry. But most important it can be said: just as the old technology did not replace the artist, neither will the new                                                                                                                                                                                         CLASS 04.3
                                                             
  1755-(014)03.4

  excerpted with permission from

  An Encyclopedia of Coin and Medal Technology

  For Artists, Makers, Collectors and Curators

  COMPILED AND WRITTEN BY D. WAYNE JOHNSON

  Roger W. Burdette, Editor

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