What is a challenge coin?
As a professional in the field of cryptocurrency and finance, I often encounter various unique concepts and practices. However, one term that has piqued my curiosity recently is the "challenge coin." Could you elaborate on what exactly a challenge coin is? I understand it's a tradition in some military cultures, but I'm curious about its origins, significance, and if there's any modern relevance or parallels in the financial or crypto worlds. Does it have any specific value, either symbolic or monetary? And are there any interesting stories or anecdotes associated with challenge coins that you know of? I'd appreciate your insights on this intriguing topic.