What is the rarest dime?

Could you elaborate on the concept of the "rarest dime" in the world of coin collecting? Are you referring to a specific year of mintage, a unique error in production, or perhaps a limited-edition commemorative piece? How is rarity determined in the context of dime collecting, and what factors contribute to a dime being considered the rarest of its kind? Furthermore, what are some examples of the rarest dimes known to exist, and what makes them so valuable and sought-after by collectors?