Seventy years ago, Gabrielle “Coco” Chanel introduced what would become one of her brand’s quintessential products: the 2.55 bag. Named after its birth month and year — February 1955 — the style is considered a landmark in fashion history for its innovative design.

The 2.55 was regarded as pioneering for incorporating a shoulder strap, a practical feature inspired by soldiers’ bags that allowed women to carry a handbag on their shoulders, freeing their hands to do other things. A feature that is seen as standard nowadays was then unseen in women’s wear, with bags being primarily designed to be carried by hand or as clutches.

“Tired of carrying my bags by hand and losing them, I slipped a strap over them and slipped them over my shoulder,” Chanel said of the bag’s creation, according to the brand’s website.

Chanel is also credited for adding feminine touches to the shoulder bag, including compartments for a lipstick and compact, and an inner zippered pocket that she deemed perfect for love letters, as previously told by WWD in 2000.

The original 2.55 bag featured a rectangular shape and a front clasp known as the Mademoiselle Lock, a name that referenced Chanel’s unmarried status. Other details of the bag also nod to Chanel’s life, including the diamond quilted leather. A signature of Chanel’s, the quilted pattern took inspiration from her love for horse riding and the equestrian coats and covers she would wear while racing.

Over the decades, the 2.55 design has been revised and reissued. In the 1970s, then-creative director of the Chanel brand Karl Lagerfeld phased out the Mademoiselle lock, introducing the interlocking CC closure. Then, in February 2005, for the 50th anniversary of the Chanel 2.55 bag, Lagerfeld launched the 2.55 Reissue, reincorporating the Mademoiselle lock. The designer also created the 11.12, inspired by Chanel’s shoulder bag.

Other reinterpretations of the 2.55 saw the style crafted from silks, suedes and denim over the years. Celebrities like Jacqueline Kennedy, Princess Diana, Jane Fonda, Kate Moss and Penelope Cruz carried the bag’s appeal through the decades.

Today’s Chanel offers a variety of bag designs, with some being inspired by the 2.55, such as the Chanel Classic Flap Bag, which differs from the 70-year-old design by featuring interwoven chain and leather straps instead of all chain-link straps, and an interlocking CC logo twist-lock instead of the Mademoiselle lock. Current offerings of the 2.55 style are priced from $5,200 to $11,700 on Chanel’s website, depending on the size.