Here's a picture of a Singletree with the chain hook. I think 3rdof8's got it although yours looks like a very old hand forged one. This is what you would have hooked the chain on to drag that Whitetail in your avatar on to drag him out of the woods.
Rather than posting the measurments, put a quarter next to it in the pic. It is much easier to quesstimate the size with a visual reference.
A actual size reference in the original post will save many a poster the hassle of scrolling up and down to guess the size of an artifact when trying to help you.