The "R" designation refers to the number of chips thought to exist. An R-5 of which no more have surfaced will still be an R-5 in ten years. The value for an R-5 small town chip will usually be less than for a Las Vegas R-5, because there are more people collecting Vegas, thus more demand of the same supply. Occasionally hoards of a previously thought rare chip may surface, bringing your R-8 to an R-2 overnight.

Dave