Hi John, We have a widely-known, published and
"accepted standard of rarity" understood by a
majority of collectors in our hobby. If I was going
to describe a chip by calling it rare, I would at
least include a few words of fact as in the sample
description below:

FLORIDIAN CASINO $25 CREST & SEAL CHIP

I consider this chip rare because there is currently
only two examples known and recorded to exist. One
is in the museum of the US Playing Card Company, and
the other is in the cabinet of a well-known Florida
chip collector.

I think the above description says a lot more than:
The Floridian Casino $25 chip is rare.

JB