Coins and currency are exactly what they are. Never retired, always redeemable. Any effort to affect their value would be an infringement on the "Powers of Congress".

All other devices that can be exchanged for goods, services or discounts would be considered tokens, coupons or checks. These can be retired, cancelled or have a predetermined expiration. To deliberately alter any of these to change their value is forgery. In fact the casinos are not allowed to cancel a chip until after the retirement process and redemption grace period are complete.