So long ago, I forget the details and which chip is which. But I bought a $1 Park Place chip from an outdoor flea market dealer, who had a glass case and all. The chip was tan. I got very excited thinking it was a rarity or manufacturing error. But the consensus was that the sunlight did it. I then put one on my window sill for a few weeks. Here is the evidence:

Robert
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DALE ROBERTSON, LINDA DARNELL with a gun and JOHN LUND (left to right) next to a gambling table in "Dakota Incident" (1956).
http://www.antiquegamblingchips.com/StillsD_Westerns.htm