Thank you.

The image is so small and the letters are so common, that it could be anything. You can try Arial Black or Helvetica Black, a bit expanded.

That's terrible advice. It's high end fashion. They're not going to use Arial or Helvetica. It's anything Gotham is a closer bet. Something with more rounded geometric, uniline letter forms. In any case it's Chanel so it's custom. Existing typefaces will only give you an approximation.

try Blair or eyecontact

Chanel has always used exclusive bespoke typefaces and even for its main woodmark (makes sense for a fashion industry leading company). For instance, on chanel.com, they're using one as webfont which is called "abchanel-couture" and looks not so far from your sample. Whatever it is called, it's some sort of all-caps extended grotesk.
Some substitutes: Presicav, Adrianna, Sackers Gothic/Engravers Gothic/Blair (as previously suggested), Turnpike, Akzidenz-Grotesk Extended, Ronsard Crystal, Sweet Sans, Fashion, Zeppelin, Doublewide, Halogen, http://Idlewid, Luxury Gold, Biondi Sans...

The type is called ABChanel Couture, it has been drawing by Steidl for the first book they made for Karl Lagerfeld. One of my favorite font.

Hmm … the typeface which was used for the first book that Steidl made for Lagerfeld was drawn ‘at’ Steidl, not ‘by’ Steidl. Akzidenz Grotesk Extended would definitely make a better substitute than Helvetica or Arial.

http://instagram.com/p/aAuAYVrmU5/

that's an important point... sorry for my english