You have to know what you're looking for, for sure... casting flaws come from things you might expect to find as a problem with say- something you put in a pan to bake that's liquid at first- but then comes out solid. So - casting "balls" and dots- where it was formed as a solid sphere from the "baking"'- usually around the edges... pockets that make "pits"'or pitting that can't be explained really as anything other than air trapped in a cast mold. Other cast flaws can include lines,ridges, or depressions that are evenly drawn throughout a piece, that indicate a flaw in the mold. It looks like a bundt cake, basically. Die flaws also exist though- where a die has worn, or has an imperfection- overstrikes and understrikes, kind of like the flaws you see in coin collecting.