What you could do hundreds of years ago-- and can still do it today-- was go to a bank and present this bond or IOU and say, "What will you give me for it?"

在数百年前你们能做的,在今天还是能够做到的就是,到银行出示这份合约或欠条,问,你们根据它能给我多少钱

耶鲁公开课 - 金融市场课程节选