You need to register with your ID card. Precious items such as silver, in order to avoid theft, the industry will also require the signing of a letter of guarantee when trading, and require the signature to declare that the source of the item is legal. If the source of your money is unknown, the police can find yourself according to your ID number. As long as it is your own money, it doesn't matter even if you provide your ID card. This is just a procedure for the public security department, and it must be put on record.