The first four digits "374 1" are the identification number of American Express Company, which is used to identify that the card is a credit card issued by American Express Company. The fifth place is the card grade, where "1" means ordinary credit card, "2" means gold card, "3" means platinum card and "4" means black card. The sixth digit is the code of the issuing bank, which is used to identify the specific bank or financial institution to which the card belongs. Different banks or financial institutions have different codes.
If you have more questions about American Express Platinum Card, you can consult its issuing bank.