Not a farm tool, but....

[Mitch]

We picked this up because it looks cool and it's old. But I can't find anything on it. It says Pat Pend The Stone Keg CO 240. I figured if anyone could figure it out it would this place!

[Northwoods]

Could we think about what it could be if the bolt were removed?  It doesn't seem to be part of the device, really.

[turnnut]

 Pat Pend had made thousands items of many types and uses.  all kidding aside, 

 is that opening of what I presume are jaws about 3" to 4"  ?

 and the bolt about 3/8"  ?
 it would seem that if you tighten the nut, it would open instead of tightening on an object.

 in the 1st picture, far right, would your hand fit comfortably ?