Many players use 36-card deck to play the game. And Russia 9817 marked card is a kind of this card. Many Russians purchase No. 9817 poker card for simple games, not played in casinos. We print invisible marks on the back of cards. Meanwhile, it can be printed small mark or big mark on the back of each card. You can not read the marks by your naked eyes. It is mysterious but not a big thing. As long as you wear a pair of IR contact lenses or IR sunglasses, you are able to see those marks.