German Coins

I was hunting through my coin collection and forgot I had a pair of 1941 Nazi coins. One is marked with a "1" and the other is marked with a "10". I figure that's the denomination. They are stapled in the little cardboard sleeves, but I want to take them out and clean them because they are kind of crusty. Should I? And if so how should I properly clean them? Or should I just leave them be