After Hurricane Katrina, quite a few Mississippi Gulf Coast chips started showing up that had a similar appearance to your Atlantic City chip. In the case of the Mississippi chips, the discoloration was a direct result of being exposed to salt water from the Gulf Of Mexico and a mixture of bright sun light. In fact, many chips from Bay St. Louis, MS Casino Magic were found strewn on the ground after the hurricane destroyed portions of the casino. Ask any Mississippi collector about the various chips that have been discovered over the years --two hurricanes and several bouts of high water flooding. Hope this helps.
The below example was found in the sand, washed ashore by high tides.