Impossible to say with any degree of certainty :-) Would need to see the whole tree plus both spring and fall foliage and even then it is extremely difficult to assign specific ID's. It is a grafted tree, not a seedling?

It does look somewhat reticulated so you could get some sense of what it might be by Googling images of reticulated cultivars but nothing immediate comes to mind. (be aware that unusual coloration on midseason growth is not always typical and could certainly alter the possibilities).