The challenge coins are normally produced based on stamped bronze for superior quality, zinc alloy is a preferred material for big size and more outstanding 3D, or coins with bottle opener function, iron is workable as economic material for small size of coin. Challenge coins can be customized in various shapes, sizes, and plating can be various shiny or antique gold, silver, copper, nickel, dual plating; decorated with soft enamel or imitation hard enamel, or a printed insert with epoxy coating, or with gemstones. Unique names or numbers can be engraved on challenge coins.