Help Determining Graft Union Location

Everyone - I wanted to enlist your assistance in helping me determine the location of the graft union on this apple tree. It is supposed to be an Arkansas Black on M9. I was certain when I got the tree that the lower, more bulbous point was the graft union, but looking higher I can see a clear difference in bark color several inches higher. In your opinion, is the graft union the lower or higher point?

The graft is at the lower bulbous. If the tree has an interstock to bridge incompatibility, the upper may be a second graft.graft


Awesome. Thanks for helping me out!