I can see it, but can only guess as to what it might be. On one of my RSG stocks, there's a couple of dark partial "rings" near the band spring hole on the left side. I caused this somehow from the pressure of the stud on the sling - the fastening washer on the back. On mine, it might have happened while it was in a "Sack-Up" with the weight of another gun against it. Even with a lot of slack in the sling, I doubt that the snap would reach down to where the mark is on yours. And - it looks almost perfectly centered, like it could have been caused by a manufacturing fixture. Is there something in the shipping crates that could cause a mark like that? - Bob