Bill of Exchange
  
The name of the original Silk Road Currency Shop guy.
A bill of exchange is basically a check, or written (but super legit) IOU, that’s used most by international tradesters. It’s an official document that makes one party pay another party, either ASAP (a “sight bill”) or at a specified time (a “term bill“).
If the bill is made by a bank, it might be called a “bank draft.” If made by an actual human, it might be called a “trade draft.” International IOUs go by many, many names (apparently).