Hi,
It is a good coin to experiment with. If you want to remove some of the encrustation, put a little bit of water on the spot, drop a little baking soda on the spot. It will make a slightly abrasive paste.
Use either the blunt end or the pointed end of a sandwich toothpick or a small shish kabob skewer to carefully work just the area with the corrosion. Here are some before and after pictures of a 5 pfennig piece I fooled with.
It is an abrasive cleaning and I agree with Chuck about the safety issue when cleaning. This is definitely not a safe method but you can see that the after is better than the before. It is also important to say that I do not recommend cleaning coins.
In order for me to be able to identify effects on coins, I mistreat a few along the way to compare other examples to. This one is part of my "what to look for on a cleaned coin" files:-)

Thanks,
Bill
Edited by foundinrolls
07/31/2008 3:54 pm