You can buff it out with a mechanical buffer (better), use a paste to polish (barely good) or just let it be (best). The mirror polish is not tenable to maintain, nearly any abrasive necessary to cutting grease and buildup on the copper when washing will dull the finish. Just let it be. The copper is there because it is very conductive, not because it has a shiny gold appearance.
9/1/15 at 8:29am