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?

That’s a classic trick—tiny edge notches as signals. It’s the sort of thing a historian would dismiss as folklore unless you can pull up a mint record that shows the notch was a known counterfeiting deterrent. If the 1673 St. Mark really had a “secret code” on the rim, someone would have written it down somewhere. I’d be curious to see the actual coin in a museum; a clean edge with a missing notch would make a perfect case study. In the meantime, it’s a neat illustration of how even coinage can be turned into a covert conversation.