Mack869

Just my $ 0.02 but I made an edge slicker for my dremel using the screw bit attachment and securing a multi-layer disk of leather with that set screw. Turned on dremel at lowest setting and used small round dremel stone to shape curve. The disc indentation also gets burnished and it turns out that burnished leather can burnish leather. You can also reduce diameter way down to slow rotation = reduce heat. Must admit that a small piece of wood should work also. Anyway, it works for me. Good luck !

Actually I use a dremel for burnishing edges as well as other applications beyond edging. You can create your own ' attachment' with the generic threaded shaft attachment bit that comes with the dremel. Seems to work fine for me. (Also use sanding sleeves to dress down leather edges). For large projects or burnishing multiple layer items you would want something more "industrial". As an example, I probably would use my dremel for dressing a belt or strap edge, but wouldn't on anything larger ( lack of patience ; - ))

I agree with Barehands and Bob, that looks exactly like a water stain to me. You could try casing the piece first and letting it dry in cool air (would also suggest using distilled water) thoroughly to see if contrast is reduced (wetness needs to be consistent on whole piece, otherwise you might only end up moving the issue to a different location). If that doen't help to your satisfaction, I think your fallback should be dyeing. I have never had good luck with chemical treatments (e.g. oxalic acid etc.). My $0.02, best of luck !