I don't know.
The knife's a bit of a mystery. It came from a hardware store in 1985. I guess it's possible that someone bought it, reshaped the sheepsfoot, and returned it. My best guess it that either it was a mistake coming out of Camillus, or that the sheepsfoot got damaged at the factory somehow and some cutler at Camillus reshaped the blade and sent it out. Whatever happened to it, the spear blade is expertly shaped, so my bet has always been on factory mistake or salvage. I've never seen another like it.
I've also got one of the 301s with a 319 tang stamp from the same era, so I know odd things happed on occasion.