The two values of full-value currency are equal, but the two values of nominal currency are different. Under the condition of paper money circulation, paper money itself has no value, so the value of paper money refers to the purchasing power of paper money or the value represented by unit paper money. Because paper money is circulating instead of metal money, the value of paper money on the one hand reflects the amount of metal money needed for circulation, and on the other hand depends on the circulation of paper money itself.