Anyone can buy colorless ink with UV properties and rubber stamp a casino chip. I'm not saying it has been done, but you can't rule out this kind of activity if it creates something of interest to collectors that they will pay for. I mean, some people even take out all the plastic on a casino chip and replace it with different colors... and collectors buy them .

Durability of the marking in play is not an issue as most collectors don't use their collectibles to play card games with.