Hard to tell from the pics but it can be matte blued or parkerized. Both finishes start with a bead blasted surface and the finished colors are quite simliar and park can vary in shades. You can test it by applying a drop of vinegar to a hidden area and letting it sit for 10 minutes. If it removes the finish it is blued. Regardless of what the finish is, it has been refinished, maybe to repair a pitted rust issue or just for a non-glare finish when the Magnaporting was done.