Still interesting.
My theory is an unfinished ball valve trunion made from Stellite, fired from an improvised home-built cannon decades ago into a tree, where the tree then grew over it, and eventually the lumber was split.
Think about it. If there's a nearby valve factory, and I had access to these blanks of badass metal roughly in the shape of a ball, I'd totally steal some and shoot them at stuff.
Also, Stellite fits the material properties perfectly. It's a superhard, non-magnetic, non-ferrous, Cobalt alloy that doesn't do anything with a grinder test and has excellent properties as far as absorbing heat.
The funny thing is, that theory has now been picked up a few times throughout the thread...