What penny sold for $1.7 million?

Excuse me, but could you please clarify which penny you're referring to that sold for an astonishing $1.7 million? Is this a rare or unique coin with a special history, perhaps one that was minted in limited quantities or features a notable error? I'm intrigued to learn more about the details behind this remarkable sale and what makes this particular penny so valuable. Could you elaborate on the specifics of this transaction, such as when and where it took place, and any additional factors that contributed to its extraordinary price?