The first one, the one this thread is about, was quite cheap and in poor shape, and even though I normally go for coins in much better condition and in good detail, I decided to go for it as I think it has some potential. It is an anonymous Byzantine follis (class D from the reign of Constantine IX, 1042 -1045 AD). These coins are hard to find in good shape. I was attracted by the fact that the Christ side seems to have really good detail hiding under the dirt. At least I thought it was dirt when I first saw the seller photos. In hand, the brown layer is quite thin and it is almost like a second patina on top of the green patina underneath. I thought that maybe I can end up with a pretty nice coin if I clean it properly, but again, I could be completely wrong... So, how do I go about it? Not quite sure where to start... I read many threads in cointalk from members that do this kind of thing regularly, so I am thinking of soaking it in distilled water for a few days, then deep freeze for a few hours and then gently rub it with a soft toothbrush. Is this a good start? What shall I do next?