Technically, it appears that it meets their specs. It is a piece of used gear and it is not expected to be PERFECT. If you wanted it to be PERFECT or LIKE NEW, you should have spent the extra money to receive that level of perfection.

I do not expect perfection in anything I purchase, whether it is goods from a store or food in a restaurant, it was built or prepared by imperfect people, just like me. To expect perfection means you will always be disappointed with what you get in life. I was a manufacturing engineer in an electronics manufacturing plant and few if any items were perfect in all ways. All items left our plant met their specs, but that does not mean they were perfect in all respects.

But, you are the final judge. If that small scratch bothers you and will continue to make you unhappy with the purchase then by all means return it. But remember, the unit you get to replace it (even if new) may have problems that you cannot see.

Perfection is the enemy of good enough and the pursuit of perfection is endless and heartbreaking. At some point, you draw the line and take what you got.