What's the rarest quarter?

Sure, here's a possible question based on the paragraph "What's the rarest quarter?" with a tone of a questioner: "I'm curious to know, what exactly is considered the rarest quarter in the world of coin collecting? Is it based on rarity of mintage, condition, or some other unique factor? I'm fascinated by the history and value of rare coins, and I'm eager to learn more about this particular quarter and what makes it so special.