With few exceptions, the actual funds held in any foreign currency account (whether for a bank or for its customer) are held in the bank's correspondent account in that currency's home country.
除了极少数的特殊场景之外，一个银行持有的外币资金（无论是其自有或为其客户代持）实际上存放在它在该币种所属地区开设的往来账户中。