What is this type of file called? And used for?

[Mac53]

So I know this is a file (or is it a rasp?...), but what would I call this? What is the material it is meant to be used on? I have tons of files but this is the only one like it.

[john k]

Is it coarse enough to be on horses hooves?   Farriers dress down the hoof to fit shoes.

[bill300d]

This should explain it pretty well. https://archive.org/details/NicholsonFilesForTheFarm
By the way it's a half round rasp.

[Mac53]

Bill,
Thanks for the book post and name! That was a cool look through. I didn't see this specific type of rasp though; would you just call it a fine rasp? I've never seen one with so few teeth so widely spaced.

John,
It's very fine. I know it's a little worn, the teeth are a bit bent over, but it just feels like tiny pumps when you run your fingers over it. Very fine.

[Bill Houghton]

Looks like a patternmaker's rasp - they often had fine, randomly spaced teeth.  They're pretty worn; not much rasping left in that one.

There's a place, Boggs Files, that can sharpen rasps; you might see if they think it's possible on that one.