Looks like a GSD to me (and when cleaned up he looks real nice), colors very close to my girl Kyra (blanket back, black and tan).
She was 73 pounds last time she was weighed, looked lean but solid - maybe smallish for a shepherd but big head like yours (or is that from the camera position?). Maybe some working line blood? Can you up the food and exercise, or do you / your-vet think he's in a good weight range?
In any case, he's lucky you've got him now.
Last edited by brucebourdon; 12-01-2015 at 11:01 PM.