Orpingtons have white skin/legs I think. From the body type and the look of the head I'm going to guess Blue Australorp, but they aren't very common, and they have pink/white bottoms of the feet..maybe a mix?
Blue Orpingtons have slate legs with pale whitish grey bottoms to their feet. Could be a hatchery quality Blue Orp. Don't see the same gold in the neck that you see, debid. Though I am interested in the "mutt" theory