Look for the serial number and go to
and enter the serial number. This will give you the product ID and if it's covered under warranty(contract # and expiration date of warranty).
If you go to a Cisco partner, you should not have any problems. At least I would hope not.
Best way to avoid any counterfeit product is to request support contract along with it or just ask for the product serial number in advance to buy a support contract for the same, Any Cisco partner should be able to tell you the status of product by serial number.
I always ask for product serial numbers in advance and buy from my trusted cisco partners only.