At present, the green cartoon cards (debit cards) handled by Postal Savings Bank support primary and secondary cards, and the card faces are different with different card numbers. Credit cards handled by the Postal Savings Bank also support primary and secondary cards with different card numbers. I haven't seen the card face before, so there should be subtle differences (such as multiple sub-cards, hehe).

It seems that none of the other cards support the primary and secondary cards. . .