Nanny's dollface

While my DH was walking our rescue dog, Charlie ( rhodesian ridgeback and pitbull mix) both came across a puppy ( any guess?) who followed them home.
Puppy has a collar but not tags. Once home, we leashed the puppy and walked around the neighborhood making inquiries to each person we met and rang the door bell of a home where he was found. No one answered despite 3 cars in the driveway- maybe the home owners thought we were selling something.
Right now, the puppy is enjoying himself in our backyard. Quiet as a church mouse.
I have no idea what mix he is , maybe someone on the board does. He is smart as a whip.
We have to make a decision- call animal control and bring him to the pound or keep him for a few days and see if we can locate owner by posting info. I hate to think of him being in a cage but just don't know if he will fit in. Oh well, our rescue dog paid it forward.