How do I know if these Chanel sunglasses on eBay are authentic or not?

hey there.I was just up searcing Chanel shades eBay and there are those who are really cute as I want, but I'm not sure that their claims real or seller fake.the they are genuine, but I'm not sure.how do I know? here's a link to a pair of shades that I want: http://cgi.ebay.com/Authentic-2006-New-Beautiful-CHANEL-Sunglasses_W0QQitemZ180008521576QQihZ008QQcategoryZ1063QQrdZ1QQcmdZViewItem

if they were the real aunthentic, it would not sell less than $ 50.


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