Adorable!! I'm tempted to say that he might have Toller in him - appearance wise, he looks pretty Toller puppy like, but you never know with pups. Lots of red pups with brown/flesh pigment look Toller like to me..lol. That, and my Tango has a sister who looked almost identical to him when she was a pup (minus the curled tail). I definitely don't see any Mastiff. He's sure a beautiful puppy, whatever he may be.