Alternatives of machine printed domino
Like playing cards can be marked with invisible ink, domino can be marked with infrared ink.
The invisible ink marks printed by machine is much better than the marks made by hand. High price with high quality. But not everyone can afford such a high price; they prefer some alternatives with cheaper cost, such as luminous ink for marked domino. Some magicians and gamblers will buy domino ink to make marks by themselves. They use infrared contact lenses and luminous sunglasses to read the invisible ink marks they made.
People often ask how to play domino game perfectly? Or why someone will cheat in game even at the risk of being caught? I think both of the answers are that players can see the pips of each playing cards or domino, so they can make the next move with correct decision. Few people can refuse such a temptation.