Howdy, new member here, but long time reader. I have a Bernardelli Italia Esctra with the polished metal receiver. There does not appear to be any sort of coating on the metal. There is some slight discoloration on the bottom and right side of the receiver, from being carried. I would like to clean that off. My question is what to use and not damage the engraving. I would post a picture but not sure how yet. Thanks Tom