Here is a cropped (and enlarged) extract from the Nevada Gaming Approval list. (The original is a PDF, which is hard to work with.) It identifies five plaques approved for use at the casino. They are:

$100,00
$500,000
$1,000,000
$5,000,000
and a larger plaque without a denomination given.

I will assume this to be the $10,000,000 plaque, which we know to exist (see below). Now, this says nothing of wheather or not it was in-use (or played), however, if our memories serve us well, several collectors were permitted to hold that $10,000,000 plaque and have their pictures taken (holding the plaque) when the Aladdin first opened.

I could be wrong, but I suspect the plaque to be a genuine gaming piece.

Jim