One of these coins is lighter than the others! So we brought them in for questioning! They're not being very cooperative, but maybe you can read some sign of their guilt:
The won says, "So what if one coin is lighter? Who cares how much a coin weighs?"
The austral says, "We're all different currencies, so I really don't see why we should be the same weight in the first place."
The Reichsmark says, "And have you noticed that we don't even have denominations?"
The tögrög says, "Is that why they're interrogating us instead of just weighing us?"
The dupondius says, "This whole thing is stupid. Let's get out of here, guys."
Answer Checker:
Hints: The coins are right: It really doesn't matter which one is lighter than the others. The wording "some sign of their guilt" in the flavor text is kind of an awkward attempt at a clue. The important information is the symbol for each currency.