That's a franken-mill. the base is an Atlas horizontal mill, with a vertical head installed in the overarm bar bore. Looks like the horizontal spindle was removed, but someone cared enough to block off the spindle bore. If you can put a horizontal spindle, backgear, jackshaft, and motor mount on it, you'd have the best of both worlds. It will probably only handle light duty vertical milling, but it's a decently stout horizontal mill in its own right.