This is Lurch. Based on the way he canters and gambols around we believe he is part German Shepherd and part Pony.
He is a rescue dog but we didn't adopt him; he adopted us. 4+ years ago he turned up on our patio looking like he had escaped from a gulag and has been here ever since.
At first we assumed he was just abandoned. When the vet contacted the registered owner it was the usual story "apartment too small gave him to a friend/boss, nothing to do with me". We transferred ownership and thought that was that. Then after several years we were out with the dogs and chatting to a neighbour (we only speak English, she speaks Eng + Cantonese) when another neighbour who only speaks Canto came by and started chatting to her about Lurch.
Through translation it turned out that someone abandoned him not once but three times. It seems they took him to a small island frequented by fishermen and abandoned him there..... he swam home. They did it again.... same result (now we know why he is such a good swimmer) and then they finally managed to abandon him somewhere where he couldn't find his way home (or he realised he wasn't wanted).
What a great story and thanks to you for taking him in. The best pets are the ones that 'find' you. I've had it happen to me on two separate occasions but with cats and I'm feeding a third stray now but my current cat won't let him near the front door!