Assuming this is a low-denonomination chip (say $1), I would say at a Washington State chip worth $15 to $19 is a rarity.
So if we have a Washington $1 where maybe 20 are known, currently priced in the $15-$19 range, and 50 are found, I would say that that amount would probably satisfy the universe of Washington collectors and the chip would fall into the $3-$6 range.

Of course, a Nevada $1 in that price range would not be considered a rarity, but that's why it's necessary to factor in the context. If you had a Nevada $1 which currently goes in the $15-$19 range and 50 are found, it would have very little long-term effect on the market pricing, due to the size of the universe of Nevada collectors. In broad strokes, a Nevada $1 in that price range would have, maybe, 300-400 known, and 50 more would not have significant or permanent impact.