These days you just can't tell for sure without being an expert and even then one needs to use caution.
I was looking at purchasing a used 116613 last week so I got the serial number from the seller. It checked out for the correct model year so I called Rolex in New York to see if it was on their list of "stolen watches". I was shocked when the woman on the phone told me they do not give out that info. So I asked if the local AD could give it to me to which she replied "No". Rolex wont give it to the AD either. So I replied " So the only way I can know if a used Rolex is stolen is to buy it, send it to New York, and if it is stolen you will let me know but keep the watch?" Her response was that if they run the serial number and if it happens to be on their list they will "hold it" and contact the registered owner and or law enforcement. Once the rightful owner is proven then the watch is released to that person.
So I told her that basically she is telling me any used Rolex I buy I assume the risk and she replied saying that if I purchase a used Rolex from an AD, then the AD would be liable if something goes wrong. Otherwise buy new from an AD.
I think that attitude is a crock of stinky brown goo because Rolex is playing mafia. This method of doing business ensures buyers go out and buy a new watch, or at the very least go to an AD. Not much incentive in my opinion to own a gen or have it serviced by Rolex, unless I want to pay full retail, which I don't.
I passed on the watch...I think I will buy a rep and make 18kt parts and use a movement I can service or have serviced locally.
Jeeeez Mahn.