Your Caesars AC $100 chip is a "floor sweeping" or manufacturing set-up chip from the Chipco plant.
In Chipco's earlier days, some of these type chips made it out of the factory and into the collecting community.

The four leaf clover is probably a generic type roulette chip -- white with brown background. Then the Caesars image was printed on top.
They may have been aligning their machine before a print run, or perhaps canceling an overrun of chips.

Here's the Caesars chip without the clover under/over stamp --

(Image from the Chip Guide)

You can see another example of this type of double-stamp at the following eBay auction (not mine) --

http://www.ebay.com/itm/281122316219

I personally DON'T consider this as an "error", nor do most others in the hobby, IMO. As a floor sweeping, it's an interesting artifact, but not particularly valuable at all.