I'm definitely not an expert but I've learned to spot the fakes pretty well and this one looks absolutely authentic. I've never seen a fake of the limited edition Navi 01s. If there's something not as described you can still file an eBay claim. There's really no such thing as no returns on eBay with the buyer protection policy.
I'm jealous.
This is my dream Breitling assuming I can still find one next summer when I'll have the funds available. This model is one of the most beautiful Navis ever made IMHO.