Materials used by governments for coinage production generally have to possess various functional properties in addition to being difficult to imitate by counterfeiters.  Desired characteristics include the color of the material, its ability to resist tarnishing and wear under typical handling conditions, and possibly desired magnetic properties to ensure fool-proof recognition of coins by vending machines.  Moreover, for ease of manufacture, materials are required which possess acceptable hot and/or cold workability coupled with a final hardness which will provide the desired abrasion resistance in the finished coins.  Finally, the material selection is, of course, affected by the need to ensure that the cost of a finished coin is exceeded by its face value. 
The desird combination of characteristics sought may be impossible to achieve with any single alloy.  Accordingly, it is becoming increasingly frequent to make use of composite materials wherein, for example, a core chosen for its magnetic properties, or simply its cheapness, is used in combination with an outer cladding of an alloy possessing the desired color as well as the tarnish and abrasion resistance.  When composites are used, it is becoming increasingly important to ensure that scrap produced will be of a composition suitable for remelting to produce useful commercial alloys.  Various laminates are described in the art and various processes for producing them make use of hot/or cold rolling.