Coinage as a spy tool? Oh, that’s a delightful niche. Picture this: a covert agent in 18th‑century Europe drops a seemingly ordinary coin into a banker’s drawer, but the edge bears a tiny, nearly invisible mark only a fellow operative would notice. By the next exchange, the mark is gone, and the agent has confirmed the bank’s loyalty—no telegrams, just a minted whisper. It’s the kind of detail that makes me wonder why the history books never highlighted it. Care to dive into a specific example?