Hmmm. IMO, it's most likely overstock OEM, which is why it's cheap and has no packaging. I've gotten some good deals on stuff like this. Look at all the other items the seller has listed and it looks like a hodgepodge of legit stuff...

But, it could be fake. They appear to have a good rep and return policy, so you might get one, look it over, and send it back if you don't like what you see. It all depends on whether you think the savings is worth the overall risk.