RE: Return? What would you do?
In all fairness to the seller, they described the weapon as "practically new" and not the original seller. Also they encouraged you to ask any questions of the seller. When I purchase a gun I always ask the seller questions.. any rust, condition of the bore, how's the trigger, and then note their answers. If they are evasive, I begin to worry.
That really is not a lot of rust but when you're paying good money, I can understand your frustration. If you have some JB Bore paste & patch,you can lightly scrub that surface rust off the barrel. It will remove the bluing though. Then you can purchase a blue and black marker from Birchwood Casey. At looks like a fancy magic marker paint brush. You could paint over that and it would probably never be noticed. When your done using the marker, put that in a vacuum sealer bag and seal that back up and it will not dry out. I've had my pen for a long time now. I touch up marks on my rifles all the time and it works excellent.
Check the add and see if you can return the pistol if you are not happy. It is a beautiful looking weapon there.