Determining the authenticity of a Coach handbag for sale on eBay relies on careful examination of the details of the bag. Look for such things as the serial number, the zipper, the Coach care card inside the bag, the color of the thread and the positioning of the logo.
If a seller only posts a few photos of an authentic Coach handbag, he or she should have no problem supplying more photos for prospective buyers to determine if they are purchasing the real thing. A real Coach handbag will have an "Authenticity Leather" tag inside the bag with a serial number. The color of the thread ought to match the color of the bag, and the stitching should be perfectly even all around, in addition to double-stitched, never single. Ask for photos of the underside of the zipper to confirm the "YKK" engraving; fake Coach bags have zippers of lesser quality with no engraving.
If you wish to purchase a handbag with the "C" logo decorating the fabric, the "C" can offer important clues regarding the bag's authenticity. In most cases, the tip of one "C" should touch the tip of the "C" facing it. Finally, make sure that the photos you are seeing are of the actual handbag in question and not merely stock photos.