How would i find out what bloodline my dog is, when i cant find the people i got him from?

he had papers but the people we got him from gave him to us free, or were going to charge for the papers. we took him for free and am having the hardest time figuring it out... any help will do...he's 3 yr. 62 lbs 20" head 20" tall and 33" chest, he's brindle with white chest, and socks...