Larry,

That is more commonly known as a microdot. You will find them on most $25 and higher chips anymore. I believe the technology is the same as what is used to microprint various things on our currency, the signature lines of checks, etc. They are beyond the resolution of most copy equipment so it makes them harder to copy. A year or two ago we had a good thread going about various security features.

Do you have the Harrah's Joliet Grand Opening chip? If so, take your magnifying glass and look around the tiny Harrah's logo on the boat. On the "Grand Opening" side of the chip you can read the microprinting they have placed there, on the other side there is no microprinting. You'd never know it without the magnifying glass.

Another of my favorites is the $100 from Isle of Capri in Biloxi. I attached the scan below. What appears to be a barcode is actually a microprinted strip that says "Paulson $100" over and over. The most interesting feature of this chip though is the peep hole. Just to the right of the "S" in "Biloxi, MS", you can see what looks like a tiny drill hole. That is actually a clear insert that makes it possible to see all the way through the chip.

Greg