Clashes are very common, they can be found from every mint in the Morgan series. What you want to look for are the ones that transfer letters, like the clashed E, S, T, I and N. The clash has to be really hard to transfer the letters.
The book on Super CD's just came out, so there is going to be a bunch of people looking for clashes now. I think that the really cool clashes are going to get expensive. So if you have some already, you'll be ahead of the curve.
