Peter, take a loop or magnifying glass and look where the other two inserts should be. I have a suspicion that the inserts have faded to the same color as the chip. I’m guessing the chip was altered by accidentally dipped in some type of chemical. White chips can take on all sorts of colors if they are dipped or even placed next to other items.

My other theory is that the chip is a back up chip that made it to the table.