If you thought the Himalaya Birkin was the rarest bag in the world, think again. The original prototype of the now-iconic Hermès purse—custom-made for Jane Birkin herself—is heading to auction for the first time in 25 years, set to go on sale at Sotheby’s on July 10.

The Birkin was created in 1984 specifically for the busy actress and singer after she told Hermès’ Jean-Louis Dumas she needed a practical bag for her hectic lifestyle. “I think I sketched it on a sick bag—or maybe the ‘don’t-be-sick’ bag,” Birkin once told Vogue from the front row of Hermès’ Fall 2012 show. “And [Dumas] said, ‘I’ll make it for you.'”

After Birkin’s passing in 2023, it was revealed that she had donated the original bag in 1994 to support the French AIDS charity, Association Solidarité Sida. It was later purchased in 2000 by Catherine Benier, a Parisian collector and vintage store owner.

Ahead of its auction, Sotheby’s showcased the bag in their Paris and Hong Kong locations. Benier had also loaned it for exhibitions, including one at London’s Victoria & Albert Museum. Now, the bag is back in New York and will be on display at Sotheby’s galleries from today until June 12.

Beyond its famous history—and the remnants of stickers Birkin once used to decorate it—the prototype has unique features that never made it into production. Made of black leather, it’s as tall as a Birkin 40 but as deep and wide as a Birkin 35, complete with a crossbody strap. The most distinctive detail? The front flap, stamped with Birkin’s initials: “J.B.” Now that is priceless.