Or, if he is advertising a chip as an R-10 rating he is advertising that only 2-3 are known to exist.

The seller is not doing that. He is saying "this chip is listed as......". He is REPEATING information established by acknowledged experts.
It is not the sellers place to determine a chip's scarcity. He did what he was legally obligated to do to make a representation here......he checked the book. It ends right there. He is not, as a layman seller, lawfully required to do any more than that.