"100 rings appraised"
In order to acquire this magic ring, Link will need to have Vasu appraise 100 Seed Rings. Given that there are only 64 magical rings in the game, it doesn't matter if there are duplicate Seed Rings that Vasu appraises.
When worn, the 100th Ring has no effect at all. The purpose of this ring is simply to recognize that Vasu has appraised 100 rings.