The fleshier neck and thicker coat remind me of lab. I wouldn't be surprised if perhaps mom was boxer and dad lab/boxer or something of that nature. He has a lot of boxer traits so I wouldn't be surprised if he was over 50% boxer. The reason I think Mom may have been pure at least is he looks docked and seems to me who ever owned the mom would want to dock the pups if the mom was pure boxer. Or someone bred them thinking both parents were boxers when one was actually a mix.

Always fun to guess and conjecture. Either way he's absolutely adorable!