In excellent condition, with crisp lettering and bright colours, the leaf – printed in around 1455 – has been put up for auction at Gloucestershire’s Chorley’s Auctioneers for a guide price of £20,000-£30,000. It has already seen considerable interest, according to Werner Freundel, director at Chorley’s.

“It’s quite remarkable that it survived in such a bright condition,” he told Printweek.

“[Pages] don’t come up for auction very often, so it’s very exciting for us – and for me personally, just to be able to handle a page from the first-ever printed book.”

Found in an attic in Bromsgrove, the leaf came in for valuation alongside various other pieces, and was only identified once it came in front of Freundel, the auction house’s book and manuscript expert.

“When the box was placed in front of me, my eyes widened,” he said.

“We looked at it quite carefully to make sure it wasn’t fake – but it really had just been resting in a box, unopened, in somebody’s attic for the past 50 years.”

Freundel anticipated a strong performance on the auction floor, with similar pages going for up to £40,000 elsewhere.

“We do think there will be some spirited bidding,” Freundel added.

“The vendor is quite happy with [the estimate], since it’s unexpected money falling from the sky, in a way – and they’re quite happy for it to go to a collector who will treasure it, or an institution that will be able to use it to teach the young and general public about early printing, its importance, and how it sparked [the] humanism [movement].”

Printed in Mainz, Germany, around 1455, the Gutenberg Bible was produced as a run of around 180 copies in vellum and paper.

Thought to be among the world’s most valuable books – the last complete copy was sold in 1978 for $2.4m (around £1.3m at the time) – there are now only 49 surviving copies of the Gutenberg Bible as more or less complete texts.

“We always live in hope that one of those copies might emerge from somewhere, but it’s pretty unlikely: they’ve probably been lost to the sands of time.

“Even when it was printed, it was pretty rare – and it wouldn’t have been cheap.”

The first sample sheets of Gutenberg’s bible were seen by humanist scholar Aeneas Sylwius in late 1454; by early 1455, he had seen enough to write about the amazing production to his friend Cardinal Carvajal in Rome.

While moveable type existed in Asia, and printing presses were used in Europe for woodblock production, Johannes Gutenberg’s combination of improved presses and new method for mass producing moveable and durable metal type used with oil-based inks revolutionised print, allowing for the first time the printing of book comparatively cheaply.

Until Gutenberg’s invention, books were locked away from mass-production: painstakingly copied by scribes, each book was eye-wateringly expensive and could take more than six months to produce.

Following the press’ invention, printing quickly spread through Europe, creating an information revolution that spurred the humanist movement – the basis of Western philosophy and the precursor to the 17th Century’s Age of Enlightenment.

The leaf up for auction was likely cut from an original Gutenberg Bible in the 1920s by antiquarian bookseller Gabriel Wells, according to Freundel.

“If somebody bought a Gutenberg Bible at auction nowadays, and decided to tear the pages out and sell them individually, it would be an academic outrage – a horrible iconoclasm,” Freundel said.

“But in the 20s, that was all fair – and people were excited to have a single leaf of the Bible in their library. Nowadays, you’d be run out of town for doing things like that.”