I'm well aware of how they are made, I am a casino chip manufacturer. Break away a 1/8inch spot of a black non painted Paulson. You'll be surprised. The clay color does not go right through the chip. It's only a few microns thick. Hardy any Nevada Casinos ever ordered those insert patterns in 39mm, they had good reason.
If I had half an hour to spare I would explain why.

The consignor is (was) an AC high roller. I'm sure you know who it was. Maybe you should be asking him.
He had other similar chips. They didn't concern me as they were not consigned to the auction.