If so, your copy of the first Harry Potter book just might be worth thousands.

Before the series became the bestseller we know today, then-unknown author Rowling published just 500 copies of her book, Harry Potter and the Philosopher’s Stone (Sorcerer’s Stone in the U.S.)

Now one of the copies from this first run has sold for approximately $90,000. Bonhams sold the copy at auction on Wednesday for £68,812—far above the original estimated worth of between £40,000 and £60,000, or $53,000 and $79,000.

But this wasn’t just any copy. Not only did it originally belong to Christopher Little, Rowling’s first literary agent, but also it includes Rowling’s signature. According to Bonhams, this edition also has several typos: “Philosopher’s” is misspelled as “Philospher’s” on the cover and an equipment list early in the book repeats the item “1 wand” twice. This copy also features an illustration of a wizard on its back cover that never appeared in any of the books. It was replaced in later editions with an illustration of Albus Dumbledore.

Oh, and you might be surprised to see Rowling referred to “Joanne Rowling” as opposed to the initials J.K. for which she’s become known.

Even if you’re not lucky enough to be the owner of one of the first 500 copies, owners of other early editions could still stand to earn thousands.