I would start with a magnet (even a fridge magnet) and see whether it is aluminium or steel/cast iron. If it is aluminium, does it have a coating on it? This came up a few weeks ago and the kity does have a coating on it.
If it were mine, I would look to see if any scratches have displaced metal above the surface and remove anything that has. Aside from that I would just wax it and move on. If it is uncoated aluminium, you could work through the grits and make it shiny but waxing will make the biggest difference.