That's a good guess, Holly. Thought it was a buckle when I first saw it as well. Pretty. Looks like it has some age, Victorian maybe. I would test for gold. Helpful if we could see the back side as well. There is a lot of information from clasps, etc.
It's probably rolled gold (a type of early plating). I don't think the pin back was added. Believe it is original.
Does that front piece (with the 3 prongs) rotate? Might argue for Moreother's suggestion that this was to hold a ribbon or similar.