Marked playing cards refers to the poker cards that has been marked with luminous ink or invisible ink marks for only wearing infrared contact lenses or poker IR sunglasses can see.
People like using these marked playing cards because they look the same as the clean playing cards and people can't see any marks with naked eyes. Usually these invisible ink marked decks are used in the magic shows for the magicians can wear the IR contact lenses to always get the card he need. And the audience can't get this secret at all. Also many guys use the luminous ink marked cards in the poker games for gamble tricks. With the marked cards contact lenses, he can see all the hands of other players, so as to make a wise decision in the game.
Marking playing cards with invisible ink is a technology. Only the experienced and skillful technicians can do mark a good invisible marked deck with special machine. Even with the right luminous ink, not all people can mark the playing cards well. Thus, it's better to buy the good quality marked playing cards rather than buying the invisible ink or pen.