Most of these PTACS (package terminal air conditioners) are available with several "power cords" from the manufacturer. All have a nylon pin and sleeve plug on the air conditioner end that only fits that a/c and you can get all sorts of plugs on the other end. In fact, some of these units are multi-voltage and buying different cords let you run them at different voltages.
And you can order them with a whip of greenfield already attached to a box to cover the nylon a/c connector and wires already pulled. I suspect that's what this is.
