Dh had a few fake tag watches from China, they were pretty good copies and you couldn't tell at first.
I bought him a genuine tag earlier this year, the fakes were pretty obvious side by side and not just for the weight of the real thing in comparison to the copy.
You might well be covered by eBay, but bear in mind if you file a 'fake' claim you'll be asked to prove it and generally that will only be accepted on documented headed paper. Very few people will help you there.
If you file 'not as described' you'll have to send it back to China. Yes the seller will provide a shipping label but you may find yourself shelling out for extra tracking. Finally as has been said, you might get stung for import duty too.
Personally I wouldn't touch it.