What is this tool used for?

[lfnel]

I doubt the mystery tool is any more applicable to a John Deere tractor than any other brand of tractor, car or truck, but I do know that there's a bunch of knowledgeable folks on here who have been around the block more than once. So, what is this thing used for? It seems to be made of cast iron. The only identifier on it is PAT APLD FOR cast into the recess of the underside of what appears to be the handle.





 

[Mark-Ia]

Model T Ford valve spring compressor