I hadn't see that either, Larry. Have you showed it to Howdy Herz? He had a lot of history on the older Harrahs and Harveys chip varieties.

If it's hollow, is the aluminum thin? If you press on one side, does it deflect?

I would agree it could have been part of the experiments their supplier did to try to make a $5 slot token. Didn't they have to turn down the size of the clay chip to make it fit in the right size metal ring, though? The aluminum chip could have been a way to avoid the time-consuming process of machining the clay chip and still having a token the right size for a $5 machine. Could have been just a demonstration of the idea, with the final product to be made of a more rigid (and heavier) metal.