I had a good look at the trunk, if grafted the graft usually shows a few inches from the ground. I can't see a graft but there is something suspicious to the left. I thought the bottom part of the trunk looked flat up to the arrow, if it was spliced in at a young age then it could have been grafted. A good splice done correctly can take almost seamlessly.
Or, grafting and budding!
http://content.ces.ncsu.edu/gr...
I think I'm now seeing a graft .. look between the two arrows. (Mustn't forget the number of leaf veins!)
