This item is said to have been given to the seller's husband, who worked at the U.S. Navy base in Yokosuka. The seller received it for a fee from his wife. The seller's husband has passed away, so the details are unknown, but it's believed to be a rare challenge coin from the very small SRF organization. For those interested, please consider this item. It will be shipped via Yu-Yu Mercari service with a tracking number, double-layered in an envelope, and placed in a Ziploc bag for waterproofing. Please be aware of this. The following information is from Google: This is a U.S. Navy challenge coin. Challenge coins are collectible items uniquely designed to represent organizations or special events. They are given as tokens of affiliation or to recognize achievements. This coin features the emblem of the United States Department of the Navy. Although it is not currency, it is a valuable item to those who receive it.