A good way to test if it's a scratch or a mark is to scrub it with a Q tip or swab and some solvent or gun oil. If it comes off or fades, it's a mark, if you end up with little cotton fibers sticking to it, it's a crack.
Walt: generally speaking, if it's a flaw in manufacturing such as a cracked slide, or frame, or broken takedown levers and the like, Sig are pretty good about making things right, no matter if the pistol is used. I've had some good experiences with them with things like roll pins, springs and so on.