That's a hell of a buck. Blackies with drop tines make me drool!
If I'm questioning what made the rub, I can usually find some hair stuck to the tree, sometimes even if the rub is several months old. I've never found hair in a rub after a long winter though. My expectation is that if the rub extends much above my belly button, it's often an elk. I sometimes find that both deer and elk will rub the same tree and can isolate hairs from both animals.