Hey Charles,

Greg is right - there are a lot of different types of UV markings - some due to an actual UV printing step, other due to the pigments used in the base materials (clay or plastic), or even whiteners (for an example, check out a white T-Shirt or Gym Socks in UV light).
The UV markings on casino chips are a type of security marking - as you have noticed, not all chips have "UV" features. Those that due have names, or various sizes/shapes of the Hat & Cane (Paulson Logo); Paulson's name, BJ (for Bud Jones), concentric rings, Sombreros, Dolphins, the list goes on and on and on...

If you have a set of poker chips used for the CC&GTCC the third or fourth poker tournaments - check them out with a UV light, and you will see the initials of the person that designed the chips...

There are even known UV error chips, such as the CHIPCO LUXOR $1 chips with different sayings on both sides of the chip - it should be the same on both sides...
Another example is the Four Queen's $25 2000 New year's chip (no it isn't on all of them)

Several people have been "examining their chips" with a UV light for some time now - yes, I'm one of them, and find it interesting to see what is indeed "hidden" on a chip.

Regards,
Dick