He fits the look of a Lab/GSD mix, possibly mixed with Golden ... clearly a Heinz possibility. I wouldn't be as specific as a Mal.
Does he have webbed feet and love water? That can be a Lab trait. Some dogs will 'attack' water from a hose, but Labs tends to play with water, and usually aren't scared or angry about it. [One way to reprimand a dog is to use a squirt gun ... that can be a reward [!!!] for a Lab.]
Does he LOVE people ... a lab trait.
Is he very smart, and easy to train [ but may be independent] ? That may give you the GSD/Lab personalities.
Does he like to cuddle, does he seek out strangers, is he a sweet dog? About 10 years ago, I asked that same question on the Forum, and many owners who had a brown Lab/GSD remarked that their dog was especially sweet ... even compared to most Labs or other Lab mixes [but I'm not biased...]