I had my father in law who is a mechanic look at it and basically told me it was cast iron but I'm not sure. I've tried to find a forsure way of telling what it is. I have no idea of how to find out. I saw a video of a colonial anvil my size and style that was ductile cast iron that was tempered and the hammer ping on that guys sounds like mine. It rings with a high pitch.
20180404_130451.mp4
Maybe this can help figure it out this is a bounce test video very short