Warning: Don't try this at home!
I can't believe the casino's were that stupid to be using the same roulette chips on different tables.
I have heard of this scam many times before, usally it's done by pocketing cheaply bought chips (Many casino's will have quiet times when table limits and chip values are lower to attact punters) then returning at a different time/day after the table limts & chip values have increased. The same table is used, so the chips match the tableset and the total amount of chips is correct for that table, should the casino suspect and decide to do a stock check. The chips are then usally wagered rather than redeemed, on various and many multible combination bets that provide the lowest risk. This is done to make it as differicult as possible for the casino to keep track of how many chips the scammer has. Winning chips are then redeemed.
Some people have gotten away with this for long periods of time making thousands but eventually they all end up in jail.