I agree with the previous post....I am from the UK, when i worked in the 5 star hotels we always had tourists bring in money that was out of date. They had taken it home and found that 15 years later it was no good or like 2000 when they changed to the Euro you only had 12 months to do it and many did not know until too late.

It also happened to at the MGM when I worked there, a guest would come back 10 years later and try to cash an old chip in, most of the time the cage would take it but not always. So they would leave it as a tip and then the staff would try to sell it for what you could get!