I was excited too. But then I had many people saying it was from sunlight or heat, or both. I was skeptical, so tried my own experiment and left a chip on my window sill in my office.

To my dismay, I had to admit it was the effects of the exposure to the sun. It took the better part of a year, but it certainly changed and got much darker. I have have the experiment chip and the Bally's chip around here somewhere.