The Authenticity Guarantee service on eBay involves professional authentication by experts from the Gemological Institute of America (GIA). When listing an eligible item, it will be marked with an Authenticity Guarantee badge. If purchased, the seller will ship the item to the authentication facility for a multi-point inspection process. The authenticated bracelet will then be shipped to the buyer with expedited shipping and signature confirmation, with the cost of authentication and shipping covered by eBay.