The info in the other reviews is excellent.  I would like to add my two cents as an avid collector of Coach Bags.

Unfortunately, if you are buying one on eBay you cannot touch the bag.  To me that is the ultimate test. I can feel the quality of the leather immediately.The next is the smell of the bag.  I'm not weird but anyone who has ever gone into a store which sells leather products the smell is overpowering (and wonderful!). I know when I buy a Coach in "a not Coach Dealer," I will smell the inside of the bag. I have to be impressed by the smell; Coach chooses quality leather and that's what you are sniffing for.   I'm also looking for the patch. You MUST be able to read everything on the patch: all the words should be legible.

The tag is oh so important!  I will not carry a "Coach" bag if it does not have a tag. Most of the tags on the larger bags are on thick piece of leather with "Coach" impressed on both sides.  Some of the smaller items, like a make up bag might have a thinner tag that is two pieces glued together.

One other test is the zipper. Coach chooses the finest zippers and they should open and close with east.

The larger bags may need some waxing on the zipper, but for the most part those zippers are heavy an work well. Look at the way it has been sewn in; all stitches are even, tight and tidy.

Well theres my two cents:

Hoosier1818

Check out my bags in about a week. I have both real and copies.  I will tell which is which!