I have a roll of these coins with various dates that the previous owner described as "Die Cracks". I've come to think of die cracks as lines of raised copper (in a cent anyway) that runs from the rim inward. These "die cracks" look more like the placet cracked due to bad metal mixing, too much die pressure, whatever. Does anyone know of this kind of error and if it is collectable or are they just trash coins. The damage does appear to be there prior to or during the minting process. I'll include a few examples.
These are "lamination cracks" and "lamination peels". The metal is flaking and peeling as a result of impurities in the alloy. Quite common and not worth very much, especially in circulated condition.
There really isn't much more to them. Certainly some issues, like war nickels, are very prone to lamination errors. But they exist in all solid alloy coins. They may even occur in outer clad layers, but this is very uncommon. You might want to buy a copy of The Error Coin Encyclopedia (4th edition) or the Official Price Guide to Mint Errors (6th edition).