A galley of Sylvia Plath’s only novel, The Bell Jar, is due to be auctioned off in London later this month.

The proofs, which are from 1962, apparently include more than 70 textual variations from the published 1963 edition. In at least two instances, the novel’s heroine is identified as “Miss Lucas,” the pseudonym under which Plath first published the novel. Plath expert Peter K. Steinberg notes that these early editions are quite rare: “There aren’t many around,” he says. “I’d say in the dozens, rather than in the hundreds.”

The proofs had been on a bookshelf in a spare bedroom for the past 25 years, until the owner, who blogs as Lucy WithaY, was looking around on eBay and the book “popped into her head.” She says she bought it from a secondhand shop in 1985 when the novel was assigned to her in a college course.

“I remember buying it, but not how much it cost. It can’t have been much, because I never had any money as a student,” she told The Guardian. “I asked the chap in the shop what the ‘not for sale’ note meant on the front as I was slightly anxious I might be buying something a bit dodgy.”

Matthew Haley, the head of the book department at Bonhams, says they’ve set a guide price on the edition at £2,000 to £3,000. “It’s relatively unusual for things to come to us from people who don’t know what they’ve got–mostly people do, and they’ve inherited them, or bought them deliberately,” he said. “To end up with it by accident is rather fun.”