Bank notes that are not legal tender for all debts public and private are literally worthless. The entire point of a currency is you can trust them to have the

Bank notes that are not legal tender for all debts public and private are literally worthless. The entire point of a currency is you can trust them to have their value anytime anywhere within their region(s) of circulation. (Yes, I'm using American language to speak of European affairs, but that is beside the point.)