When I got my used 681 and cleaned it up, I noticed the faint remains of red paint or nail polish on the back ramp of the front sight. I have since recoated that with some red nail polish, but I am wondering if what I found when I first obtained the 681 was something applied by the factory or the owner. On my 686 the back ramp of the front sight has a piece of fitted red plastic, which I assume was done at the factory.