Very cool!
It looks like you can see the remainder of the limb it was hung over. As the tree grew out (diameter) it pushed on the antler a little, forcing it more "upright" until it finally started to grow around it. Now the hanging limb is little more than a knot and the tree is claiming the bone.
I imagine somehwere out there is a hunter that hung a shed in a tree so they could pick it up and carry it out at the end of the day. Either couldn't find it again or was led in another direction by a good bloodtrail.....
And what do you mean easy? I'm with Ray, I've been looking on the ground - now I have to look up for antlers? This keeps getting harder.....