I'm no expert when it comes to plating losses and brassing and rust etc.maybe someone else could tell me if these brown stains in the last picture will come off it?
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I would say that those brown spots are where the brass is showing and the plating came off. Take a look at these before and after pictures of a Gillette Slim that I cleaned up. There are a lot of brown spots on that Slim where the plating came off.