The issuing bank would be driven out of business if it didn't. They all were using fractional reserve banking so if you have a big player that's demanding gold from you you're in trouble.

发行纸币的银行将会被驱逐出银行业,如果它不这么做，它们都采取,部分准备金银行制度，所以如果你有一个对手,一直向你索求金子，你会陷入大麻烦的。

耶鲁公开课 - 金融市场课程节选