Christine, here is a list of the $200 strikes which I have noted throughout the years that have no numbers on them. By the way, I have emailed IGT to ask them to number the new ones coming out for the sake of us collectors. Some ruthless people may try to sell a stolen strike, etc. I emailed my plea to Ed.Rogich@igt.com.
Bill's Lake Tahoe "Year Round Playground" (2004)
Caesar's Tahoe "Cleopatra" (1995)
El Cortez "American Pride" (2004)
The New Frontier "Las Vegas Strip Estab. 1942" (2004)
Slots-A-Fun "Statue of Liberty-Flag" (2003)
Treasure Island "Siren" (2004)
Note also that Prototypes also have no serial numbers on them.