I bought two 690 se the first one i got ended up with the scuff lens and the second one i got they finally made changes and the protected lens is not scuffed. I rather not have to send it out just for a lens change. So I figured out how to very safely take the scuff out and in the end actually produce a even better finish on the lens then what was originally on it.
You will need
Brasso, Dremel Tool or Dremel Like Tool, The Cue tip style Dremel polish toolbit. Get the firm one not the ultra soft polish toolbit. Any kind of clear liquid wax. Like Eagle one or such. The wide style masking tape.
1. Take the wide style masking tape. Tape around the far outer edge of the lens and tape off. Making it flange out so that you dont get any splatter any where else on the detector.
2. Once tape off. Apply a small amount of Brasso to the lens. Evenly spread it over the scuff area as to reduce splatter.
3. Turn on the Dremel with polishing toolbit in. Let the Dremel rpm get up. Now starting from the left of the scuff. Put the Dremel on the lens and go back and forth over the scuff about 2 or 3 times. (Do Not stop the Dremel in one place always keep it moving.) Then get a wet rag wipe the brasso off see if the scuff is gone. If it's not then repeat steps 2 and 3 but proceed with even more back and forth strokes. Until scratch is gone. If you want to produce a even better finish on the lens. You can also polish the entire lens doing this technique. Apply Brasso evenly over the entire lens. Just start at the top of the lens go back and forth until you work your way down to the bottom of the lens.
4. Once done with polishing take a smooth rag and spray some liquid wax on the rag. Now in circular motions apply the condition rag to the lens. Do this until the lens produces a spectacular glass like finish.
Once done take the tape off and let the detector sit for 30 minutes for the wax to soak in.
After that you should have a super smooth and scuff free lens.
Let me know how it goes with yours. I hope this has been helpful.
Brasso is a very light mild abrasive that refines down the surface. It is much safer then using a super light grit sandpaper.