Well, a handwritten pedigree from a true dogman, I would trust. We have received two dogs with handwritten peds from our uncle(JW Truett) and those I know are real bulldogs. Our Boudreaux female, came right from Floyd with a single reg form and that I trust. However, just because someone claims to be a dogman and has a few years into the breed...that does not make them or their dog's legit. If a person is breeding and selling to the public, even on a limited basis, they should have registration papers, IMO. Regarding rescues and back yard bred dogs, I think you could possibly get a pure one. I know some of the dogs from rescues look better than a lot of the "breeder" dogs.
Also, what about scatter bred dogs with all kinds of different bloodlines but they were ALL APBT ... you ever heard anyone call "that" scatter bred dog a mutt? ... it's not always a derogatory term, sometimes just an agreeable euphemism or expression.