Acting Secretary of the Navy The Honorable BJ Penn Challenge Coin. Coin is approximately 1.75 inches in diameter. I sell high quality, desirable, collectible challenge coins. If you are looking for a specific coin for your collection, as a “memento” from a previous unit, to replace a coin that was lost, or for a gift, there is a good chance I may have it so please check my other listings! General Information & Frequently Asked Questions – Please read before you message me. I will not respond to any questions in regard to this policy. For any questions not covered above.