I can't remember ever seeing an American-style
roulette chip either that wasn't the same on both
sides. It's common in Europe, though, especially in
Germany, where some roulette chips will have a
picture of the wheel on one side along with
additional text.

Some of the newer (American-style), generic roulette
chips in Germany have series of animals or designs
that are translucent when held up to the light (see
page 12 in my guide). It's kind of a laminated core
like the H.C.E. type produced for the Aruba
Americana years ago, but molded to where the color
center shows through. I believe they were made by
one of the German or Spanish chip manufacturers.

I also rembember some of the remote casinos in
Argentina and Paraguay having encapsulated paper or
foil centers set into a thick plastic with different graphics on both sides. (see page 15
in my guide).
JB