Christoph Physical Maestro cards are indeed a bit unique because they do not have their PAN (the card number) printed on them, only an IBAN of one of your accounts. For Maestro cards, you need to rely on the expiry date and the description that you have chosen to be printed on them.
If that's not enough information to be able to discern them, then you could for example go to some supermarket with self-checkout, freeze all your Maestro cards except for one and then try to pay with one of the physical cards. If it works, then the card you hold in your hand is the card which you have not frozen. If it doesn't work, try another card. Then repeat the process until you have clarity.
Or ask support for help, whichever you think is more convenient for you :D
