Casino USED to use UV mark to check their chips and tell the difference of counterfeit chips but not anymore as most companys making counterfeit chips have learnt the same tenologic and able to make chips with UV mark. So it's not secure anymore. I believe when they making the inlay, they print the inlay graphic first in a big material and they apply the uv ink layer on it then the transparent layer. So the UV mark can be anywhere of the inlay.