There are only a few fake Abercrombie and Fitch items on Ebay. You can tell from the moose is smaller on some items and the tags should have one which has a pin that is attched to the item. All Abercrombie comes in a bag with abercrombie and fitch on.
As well, Abercrombie and Fitch should be of high quality and if isn't then can also be fake.
A&F items are not cheap so don't expect to get a bargain, it could be too good to be true.