I just bought this vintage rolex oyster precision royal 6426.
It is gold plated which the seller says is factory and it is engraved with 40 microns in the caseback. My biggest concern is the lack of serial between the six o'clock lugs. Instead there is two small stamps. The rest of the watch, the feel and weight all feels like it should. My guess is that it's an aftermarket gold plating if it's real.

Pictures of the inside:[ATTACH...

Authenticity Check Vintage