First-time Chanel buyer, and I'd like not to break the bank. I went on eBay and saw this black number: 120118001783 (I don't know how to link to the auction, but just go to eBay and type in the auction number under "search") Is is too good to be true? What questions should I ask the seller to verify authenticity? She says the bag was a gift and doesn't have any receipts. Are there serial numbers, details etc. I should ask her about?