Mark its not a knife it actually is a file.There use to be an old saw mill on the farm and I've dug several of those,I to thought they were knives made from files.until I sand blasted one and seen it was just a file.Got to asking around and several of the elders told me they used them to sharpen crosscut saws.By the way that ring is a once in a life time find buddy.congrats
It would be called a "cant file" I have made a few knives out of files I've dug mixed with other junk. I'll try to get some pics and post a thread about them sometime.