This puppy showed up where my wife works. The vet says no chip. We've posted on the local Facebook page that we have him and to come get him if he's yours.
Theories on what happened:
1. Escaped from someone's yard. This doesn't seem likely since he sticks around the house - he's not a wanderer.
2. Last of a litter someone couldn't find a home for, dumped in our area ( which unfortunately happens a lot).
Too big and rambunctious for someone in an apartment, dumped.
We think we've found someone to take him, if the actual owner doesn't show up in the next week or so.