I've never seen it in that color before, I would definitely take it to a Bottega Boutique and hopefully they can tell you for certain that its authentic. I just bought a navy knot clutch from a ebay seller and its beautiful. I will definitely be posting pics when I get a chance to take pictures of it. In case you are a looking for a legitimate ebay seller of bottega, the seller that I bought from is thedenimcorner. http://stores.ebay.com/TheDenimCorner
Good luck.