Wow, of all the amazing luck! I just met a visitor from a magical world. He was able to use his magic to establish common communication, and after a bit of talk he decided he wanted to bring some stuff from my world back with him, so we worked out a deal.
I went shopping and purchased a few hundred dollars worth of various goods, and he gave me a rather large pouch of gold coins in return, then departed. With the price of gold being what it is, I'm rich!
...maybe. The thing is, these are coins. Disks of what appears to be an alloy of reasonably high gold content, stamped with the image of some guy who I assume is a king on my visitor's world, and a bunch of what appears to be writing in some script I've never seen before. If I try to sell these to a gold dealer or a coin broker, it will almost certainly invite questions that I don't want to answer! Of course, I could always try the black market, if I knew how to find such an institution, but I'm a reasonably law-abiding citizen and I'd prefer not to have to deal with criminals. (Besides, even if I didn't get them stolen outright, I've heard that you tend to get a lot of the price taken out as various underworld-security fees, and I don't want that; I want to be rich!)
What strategy would allow me to turn the gold coins into the maximum amount of dollars with a minimal level of risk of anyone asking questions about where they came from?
Example (to demonstrate that question is not specifically about character action):
Two countries come into contact for the first time. Country A uses fiat dollars, country B gold coins. People from country A are unfamiliar with country B's coins. Recently country A has had an influx of tourists from country B who try to buy things with gold coins. When a merchant in country A sells goods or services to a tourist from country B, how would he go about exchanging the gold coins he receives for dollars?