Just received this really cool little travel timepiece as a gift from my Dad. He said it has lived in it's box for a quite a while, as a result some of the leather has left a mark on the case back. Does anyone have any advice on how I can clean this off the metal? Is it a DIY or should I be seeking professional help. I tried search but almost all the results I got were on how to clean leather straps! I've never had a Montblanc before and really like the look of this piece, it's a unique (somewhat kitschy, but still cool) little piece. The alarm reminds me of the clock I used when I was but a schoolboy. Any cleaning advice would be much appreciated.