While I have a full set (same serial number) of these Flamingo HILTON, Laughlin, NV, Cool Bird, Limited Edition chips, I also have a matched number, sub-set of 4 chips (the other 8 have never been in my possession). While looking to see what 4 chips I have, I noticed something peculiar on one of them.

Look at the serial numbers of these two examples. They are in different fonts. Of the 4 chips I have from this set, 3 are like the one on the left and the forth one is different.

The set shown on ChipGuide are all the same and match the font on the left.

Interesting, eh?