There are 14 UV codes on Luxor chips. Some have different codes on each side. Here is a list:
Egypt / blank
Egypt / Egypt
Nile / Nile
Luxor / Circus Circus
Luxor / Luxor
blank / blank
Tut / Tut
Circus Circus / Circus Circus
Pyramid / Pyramid
Pyramid / Nile
Nile / Luxor
Tut / Egypt
Tut / blank
Circus Circus / Pyramid

You can't miss them with a standard UV light.

The newest rack has nothing on them. In June when I bought a rack I only got 15 – 20 UV marked chips out of 100.

Thanks Paul Donohue for the list (archive link below)

http://www.thechipboard.com/cgi-bin/tcbarc08/tcbarc08.pl?read=225622