I was bragging about this kind of special 1930 solid gold with metal and white marble like dial. Last time I looked, 10 years? it was near perfect. The metal which may be 2 color gold alloy is fine, but the white grainy areas are going brown. Maybe at time of purchase it had been cleaned with something that left a residue now visible? Suggestions for cleaning? The white areas going brown are not textured metal, not an ordinary paint; i guess i need to identify what it is. The first 70 years appearance looked like new. 10 years mostly in a bank vault was not good for it.