Is this just a part of a piece of equipment or is it a tool?
That is a part for a grain binder. It is listed as a (Knotter hook with jaw). Also used on rice binder.
It is most commonly known as a bill-hook (not to be confused with a billhook or a bill hook), see: http://billhooks.co.uk/what-is-a-billhook/
Thanks!
That looks like a good potential prank "yeah john, it's a picture hanging hammer...And, sure you can barrow it."