I think you might be headed down the wrong path here. I think it's a tool used when making fence to wrap VERY tight wraps of fence wire around itself.
How it's used. When making fence and starting from a new corner, the wire is wrapped around a new corner post, and the most efficient method of attachment is to tie the wire onto itself. Take a length of wire wrap it around itself once or twice. Take this apparatus and hold it so the right side is vertical, (rotate the top to the right) move it so the base of the "U" is touching the wire, then rotate the top back left. The device will swing on the horizontal wire. Slip the tail of wire under the hook, and simply rotate the tail (left end) around the wire. The tail will wrapped wire will be very tight and clean looking.
I'm not sure about the hooks on the end...ours didn't have them...but it looks like it would be for leverage when rotating the device....it was a thumb killer! Number 9 wire does take some effort to twist.
I would love to have one of these...my dad and I used to build about a few miles of woven wire fence each year...I'd love to be able to do that again....