Definition

• Diameter.  The measurement across the widest part of a circular numismatic or medallic item; usually expressed in millimeters, or in English speaking countries, in inches. In Europe diameter is called module and is expressed by the symbol ?.  Scales other than millimeters and inches have also been used:
  American Scale.  A figure expressing the total
  number of sixteenths of an inch (a 2-inch medal
  is expressed as 32). Somewhat obsolete at present.
  Mionnet Scale.  An irregular scale devised by
  French numismatist T.E. Mionnet in 1805 grouping
  all coins and medals into 19 arbitrary sizes
  ranging from 8.9 to 78.3mm. Completely obsolete
  now, it lacks scientific accuracy.
  Today all coins and medals are expressed in metric millimeters throughout the world. Sometimes the aliquot measurements of inches and fractions are given in British and American catalogs for comparison.  See Breen, Metrology.
  The diameter of a coin or medal is formed by the collar used in striking, or the function of trimming. Coins are all struck within the restraining collar and limits the amount of lateral expansion of the struck piece. Medals can be struck with or without a collar, the later are trimmed after being struck, on a lathe for large medals, on a punch press with a trimming tool for small medals.
                  Rules For Measuring Medals               
                                                            
       The following rules exist for measuring            
              medallic items:                                    
                                                           
  ?            For those medallic items which are not round –    
              oval, rectangular, irregularly shaped – measure-  
              ments are always height by width.  Height is       
              always given first.                                                                                         
  ?            For these irregular shaped medallic pieces, think  
              of them in a box: the inside height of the box must
              accommodate the tallest vertical measurement; for  
              the width, the exact widest horizontal measurement.
                                                            
  ?            For irregular shaped medallic models diagonal       
              measurement or longest dimension (abbreviated      
              l.d.) measurements are made in planning to cut     
              the design on the proper size diestock.            
                                                            
  ?            If the design has protrusions beyond the edges     
              (hyperdimensional), these are included in the      
              measurement (as, say, a longest dimension).        
                                                            
  ?            For those medallic items with loops, hangers,      
              or other suspending hardware, these are            
              disregarded when measuring, irrespective of how    
              they are attached.                                  
  References:                                                                                                                               
  NE40 {1984} Junge, p 169.
  NC12 {1988} Breen, Metrology, p xiii.
  N20    {1998} Bowers, Appendix VIII, p 413-414.

  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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