Yugi vs. the Rare Hunter (2)

At the end of the duel, Yugi goes through the Seeker’s deck and rips up a card he says is a fake. How did he know the difference? Yami (or Yugi or whoever) just noticed that there was some sort of marking on the cards. He found out that there was ink on them and saw that he was cheating. Kaiba noticed too.

About the summary, Alpha the Magnet Warrior only got a power boost of 200 from Summoned Skull and they both attacked together for the win.