Other Considerations
One feature of challenge coins is it takes a conscious effort to carry one at all times. Traditionally, rules of a challenge include a prohibition against defacing the coin, especially if it makes it easier to carry at all times. If the challenge coin is attached to a belt buckle or key ring, or has had a hole drilled in it to attach to a lanyard, it no longer qualifies as a challenge coin. A safer place to carry a coin is in a pouch worn around the neck (like the pilot in the legend).
While coins range dramatically in diameter and thickness, a Pocket Coin normally measures 38mm x 2.5mm thick, while a Presentation Coin or Medallion is traditionally 45mm x 3mm. They come in all shapes, from square, oval, multisided to one which replicates a "dog tag".
There are many finishes available – from a simple pewter to 24K gold. While there are only a few base metals, the patina (finish) can range from gold, silver, nickel, brass, copper. bronze plus the antiqued variations. Soft or hard enamel or a printed inset with an epoxy coating may add color (the epoxies are often more resilient and scratch resistant than the metal surfaces).
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