I know what this is....

Anybody that doesn't know have some fun guesses? Don't go looking up any of the writing....That's cheating!

 I know its use but I'm sworn to secresy.

The one just like that we had on dad's ranch, we used to cut the horns off the cows.  Terrible bloody operation and I will guarantee will make the toughest hombre flinch and squirm a little.
Mel 

I reckon it's for dehorning also!
Graeme

I picked up a similar set for my nephew who collects vet stuff last month. As a kid on the farm we used them. Guess I had a stronger stomach then. Not a pleasant memory.

Yep! You're all right. I kind of expected it to be harder.... I'll have to find something more obscure. I was told it is called a "De-Poler" ...anyone know any other names?  You'd have to be a big guy to use one of these for very long! Weighs about 16lbs

Thats gotta hurt, ouch.

I have a pair of these in the barn, but never seen them used.   The veternarians I have observed at vaccinating time have used a hacksaw, or backsaw, still kinda messy. 

De-poler-  Hmmm! I know Herefords that were bred to be hornless are called Polled Herefords.

If you do a Google search for "cattle dehorning" and then click on the Images section on the left side of the page, you will see your tool at work.  Other tools simply scooped the horns out and others burnt them, there is also a chemical method.
Mel

In the UK horns were burned off young calves with a hot iron, still done today with electic models (like a large soldering iron) only painful if you touched your hand with it (sorry, poor joke!!) - polled is a term for horned cattle in the UK (not to be confused with a pole axe, used to stun cattle prior to slaughter). Similar action tools can be found as garden secateurs, but usually much lighter in construction, and using levers rather than a rack and pinion.

modern ones are a lot lighter and somewhat better.