So for those wondering, one of the reputable traders I’ve spoken to says there is a “case seal” of some sort that breaks when you open the case back, but it can be replaced when closing the case back and if done properly, won’t be noticed.

Only way you find out is when you send it into Rolex. I won’t be surprised if most of the watches that’s been to a trader already has the Rolex warranty voided without the current owner knowing.