[Rado63]

The person doing the authentication work would have to have access to the movement and when the watch is opened the authenticator would need access to what a real Rolex movement of that caliber looks like in terms of metals, finishing, screw colors etc. Do they have access to such information? Then the watch would need to be closed and water resistance tested. Does the authenticator provide that? What if the Ebay authenticator said the watch is authentic and some years down the road you send the watch to Rolex for service and they reject the watch as not authentic. Your authenticity guarantee is only good during sellers return period. So what would you do if you found something negative in the future? Best is buy it and send to Rolex for authentication or service to be sure or, If you have reason to believe the seller is reliable and experienced, then you are probably fine and have nothing to worry about.