My guess is that you may have identified this item yourself as a latch plate, it could've been on a purse or similar type item, I'm guessing here but it looks likes it would works much like a briefcase latch where you would have a second piece either on a piece of leather or a metal hinged piece that had sorta toothed or barbed hook/s that fit into the holes in the latch plate, the pivoting portion I think would've been spring loaded and would latch when the "hooks' were pushed into the holes on the latch plate, it hard to tell from your pictures but I would think the "small tang" you mention would extend out from under the plate to release the hooks.