In addition, as long as the holder goes to the issuing bank, the issuing bank has the responsibility to give the holder the equivalent foreign exchange "on demand", so the bill number is also a kind of statistical and anti-counterfeiting information. Coins are usually issued only to facilitate the daily transactions of ordinary people. Without the support of foreign exchange reserves, international exchange cannot be carried out.
If it is no longer used, it has no legal value. Because there is no promise to "pay with coins", there is no need to code coins. The current numbering seems to be completely continuous. Can you consider adding something like "check code"? But it doesn't seem to have much effect. Criminals can forge it. When checking a banknote, even if the money detector is connected to the network, it cannot be confirmed that the banknote is the only real banknote, because the banknote is not connected to the network.
There is a code on the paper money. No matter what the face value is, the code is necessary. Why are there no codes on coins, only codes on paper money? Because there are fixed foreign exchange reserves and the circulation of paper money is also controlled, it is a very convenient method to calculate the circulation by code. In addition, the serial number of banknotes is also used for anti-counterfeiting information. As long as you hold paper money, you can exchange the corresponding equivalent foreign exchange.