After seeing those last 2 pics---I've changed my mind--you are right--he is a mix--now I'm probably almost as curious as you are but it is part boxer I am pretty sure of that----No matter, he looks like a 'cool' dog anyway and it would be nice to know what else he is for health reasons, etc. And being a mix--he is probably healthier! But you will love the 'guy' no matter what he is!
One more thing, lol ! I can remember w/the boxer I had---at least w/out a boxer face--you will not get all that slobber they can fling when they shake their head!