Well, thank you for the info, but I don't think it quite matches up. I can confirm that there are black border and white border cards within each series, but I see no evidence that the same player/card is available in both colors. It's just that they took half the cards and made them white, I think, and the other half they made black. And the numbering on both colors follows the same format I used above, without a C at the end.
And I definitely have--as one example--a card numbered "OL01 187/240" and another numbered "OL01 187/240C". Both with black border, same player, same photo, etc. Now most of the card is in Japanese lettering, which is not in my wheelhouse, but from what I can see the only differences on the two cards are a)the number I typed above having a C at the end, and b)the code that players are supposed to enter into their computer/phone to play the game; that entry code is different on every card printed, of course.
I don't have any inserts for these sets, so I don't know about those. I just have the "normal" cards and the "cards with a C".
If your friend knows of any resources I could investigate, let me know please. I'll try to dig some more, as well. I may even try reaching out to Bandai.
Thanks, both to you and your friend.
Kent