That's handmade by a blacksmith, could have been used for numerous straps.
2 3/4 might be for canvas strap and too wide for a belt.
I thought it might be for an old Trunk but most leather straps are 1"-2".
On second thought, I'm gonna go with a Handmade Blanket Pin!
If it was a buckle there would be no reason to put a dip in the metal on
the right side it would have been rapped around like the lower left corner.
good luck