Many playing cards have four side white edge around the back, which is a good advantage for some poker cards. Why? Some playing cards have backs of very complicated patterns which is very difficult to make clear marks on it for contact lenses to see. Then we can consider marking invisible ink marks on the white sides.
Our technicians can mark the 4 white corners with tiny marks, including the numbers and suits. Though the tiny marks at white corners are not as big as those big marks in the middle, they are very clear to see in a certain distance for the clear black marks in the white area. Usually when it’s difficult to make clear marks in the middle for special patterns of the back, people may choose to make marked cards with tiny marks in the white corners. And in some special games that people may hold the cards in hand in a shape of fan, people can wear contact lenses to see the marks in the white corners for the overlapping cards with only one corner visible.