I had a scratch on the flat of the frame of SA SS 1911 near the barrel bushing, it was in an area that was polished. For the record, I made the scratch while doing a melt job on the barrel bushing and area around the muzzle on the frame, a little (very little in attention) and I had a nice vertical scratch. So I took wet/dry automotive sandpaper starting with 600 grit and working up through 2000 grit, always wet, and you can no longer find the offending scratch and it perfectly matches the rest of the gun. Much elbow grease and lots of patience. YMMV, but it worked great for me.
And the melt job looks good too, showed my friend and he thought it was factory done.
Just be careful if you do decide to trying and polish it out, I am one of those people that if it doesn't turn out perfect, I chalk it up to a lesson learned and go on, as long as the gun is functional and safe. Just make sure that you are comfortable if it doesn't turn out like you planned it or plan on sending to have it refinished professionally.
Good Luck!
JohnnyOrygun