I think thats the only way. On one side the chips are practically worthless later but when they dont exist anymore one might demand the full price back. Regardless of the actual times worth. I would not take that risk. Instead, if the chips have no target, i would make a list with the owners and store the chips. Its the buyers fault if they dont care about them. But it would bee too risky to give them out of hand i think. They most probably wouldnt bring in much via auction anymore.