The con tricks are as old as humanity, even if they take different forms in different eras, but the ground problem is the same: if someone approcaches you and claims to be e.g. an important noble named such and such from the overseas, they could very well be telling truth—or they could be lying, and there is almost no way to tell for certain, even though there are some good heuristics (their wealth is one, as you allude to).