Marley went to the vet and is now up-to-date on his vaccinations, heartworm negative, microchipped and neutered. He is slightly underweight at 62 lbs, since he should be closer to 70 lbs. But Marley is eating well and should gain weight without any trouble. And we were very fortunate that the vet who cared for Marley already knew him! Dr. R. said that Marley had been brought to her last year after having been hit by a car. Because of the accident, he lost a toe on his right hind paw; however, it doesn't bother him at all and isn't very noticeable. Dr. R. said that she was impressed at how Marley wagged his tail through what had to have been several painful bandage changes. She also provided us with his original vet records and we learned that both his dam and sire were AKC registered golden retrievers.
We've gotten to know Marley quite a bit better over the last week and have concluded that he has had some obedience training. He knows all of the basic commands, including "shake". We are particularly impressed at how well he responds to "no". My husband remarked that Marley is typically better behaved than our own dogs!
Finally, I'd like to clarify why I said that Marley needs a physical fence. I don't want to give the impression that Marley is a runner.  I would say he is more of an intrepid explorer, who might sneak out of a yard if he is bored or doesn't get enough exercise. The animal control officer said that he usually went down the same street, most likely trying to follow the kids. If I could let Marley off lead in an unfenced area, I do not think he would leave me. He is extremely attached to his humans.

Marley just wants to be loved and can't seem to get enough of it!