Not a spark plug, I'm taking it tomorrow to a old machinist friend of mine. This thing is solid and very heavy for its size.
Mystery solved !! Took it to my old friend today, he took one look at it and said it was a very old ball joint. I left it with him as he has a friend in his 80's that stops in that would probably know make, and model year it came from.
Dave, I'm going to respectively disagree with your machinist friend & double down on my assertion that it's an tooth/bit from a roto-mill machine. Here's a photo showing several different styles; the one in the foreground doesn't have the adapter collar in place & the shank looks highly similar to the object you found. The tips routinely break off during use; as well as wear - picture this one without the tip & it's almost an identical profile . Gary
It is a ROTOMILL bit ! Was a foreskin for 30 years no doubt Inspector is rite . Only milling people like Inspector and I would know having been around it ! I've left many of them from my side of the Mississippi River to Atlantic Ocean. He also lives in the state where the original milling machine came from and my dad was one of the first in OH to run one. great call Inspector
I agree it does look like it, but how was it used as I found it buried on a dirt road 3 miles into the woods.