Since the last time this topic cropped up I found another photo of an original ingot, and a good illustration or two of the crucibles used to make them (which, of course, define the shape of the ingot

). The easy diagnostic feature on ingots is going to be some evidence of a former meniscus (that curve of the surface that contained liquids have near the edge) where the liquid steel met the crucible wall...here are two real ingots, three crucible shapes and some steel shot from a ball mill, you can see the complete lack of similarity!