Is this really possible? Experts are divided over whether this can actually be achieved. As this would take hundreds of dealers, rolling the ball thousands of times to prove with any degree of merit.
The general consensus among dealers, is that such a signature does not exist and any pattern is a fluke. That being said, the dealer in not looking for a pattern with their own roles as they must pay attention to the players bets at the table and the roll is simply a reflex. The fact that the dealer is subconscious of his action may be the very thing that makes it possible. The biggest problem with finding a dealer with a signature is that it would take too long to measure. Following a dealer from table to table, day after day would quickly be noticed by the dealer and the pit bosses. The very fact that they are being watched would alter the dealers spin and thus the signature. As in most experiments; the observer interferes with thee observed by the mere fact that they are observing.
Dealer signatures really can't be proven and even if they could, it would be impossible to exploit. There are just too many variables that will alter where the ball could land.
