I found this today detecting the field behind the 1780 farm house..any ideas..I'm leaning towards a door latch,but i've never seen anything like this before.
Yup, what you have is part of a Mortise latch, not a lock since it doesn't have a dead bolt. It would have been used on a closet door or screen door most likely since it would not be lockable. I rebuilt a lot of those for my old house so I could match the original doors and I'd guess yours is a Corbin, or a copy of one probably dating between 1890 and 1920 based on the way it's shaped.