Your reasonable assurance of pure bred is to have your AKC (or other reputable
registry like United or Canadian ect.) papers and pedigree. Otherwise there would be some question no matter what anybody looked like or what anyone was told without tracked lineage of pure breds for many generations.
The registration would also have to be from a registry considered reputable (of which there are very few in each country) and requires the tracked, traced and verified lineage in order to have the registration papers. Here in the US in particular many 'registries' have cropped up in the last several years that basically dupe people who are unaware into thinking 'papers' when the 'papers' do not mean the same thing at all beyond a piece of paper. It's a way for unethical people to get more money for their puppies when they don't actually have the 'papers' they are giving the impression of in many cases.
They are called 'paper' or pet registries (or worse) because it's is nothing more than a piece of paper that is only worth the paper it's printed on (that you have paid more for) and does not have the same meaning as the papers from a reputable KC that requires that lineage which is what actually shows/represents they are pure bred. Generations upon generations of tracked pure breds registered and shown in the family tree.
I could make a name right now, register it as a registry, and then proceed to print a nice certificate that says anything I want it to. I could say my brindle French Bulldog was a Boston Terrier (and people have done this with these sort of registries for fun, a joke, because you can and of course much less ethical reasons).
This would not make my dog a Boston Terrier or actually indicate pure bred or lineage in any way. I could then charge you $15 to print up a similar certificate on my computer for you and then the next and next and next ect. That means nothing but a piece of paper, not pure bred. We could not in any way ever get registration papers from a reputable kennel club like AKC that is represented as pure bred by doing something like that. Just because we said so, lol.
The 'papers' are vastly different from each other and do not mean the same thing. The paper registries are also known to be used by breeders who have been suspended or booted from reputable registries like AKC for not so good or ethical or honest breeding practices or care and husbandry. It is frustrating (among other things) to watch so many get sucked in and be mislead by the impression of 'papers' and 'pure bred' that are not, so now you know not to be fooled by something like that. :-)
If they don't have papers or even aren't pure bred it still doesn't effect their ability to be a good pet at all. That is just all they are meant to be. If it doesn't matter before/when you get a puppy and you didn't go looking for a responsible breeder (tracked and verified lineage is required for that) and pups with those papers that mean pure bred it doesn't make a huge difference later and makes no difference in being a great pet. They don't need to be pure bred or have registration papers for that and that is what really matters.
Here is the breed parent club so you can get more information on the breed, breeders, rescue ect. But there would still be some question once a line is no longer accurately tracked and appearances can sometimes be decieving and of course, people aren't always honest. A lack of proper and accurate registration papers is often a first hint and red flag number one when looking for an actual good, responsible and knowledgeable breeder. You might check petfinder if the registration isn't as important to you in your search for a companion and often huge savings as well. Good Luck. www.thelabradorclub.com
members.tripod.com www.wildheirlabradorrescue.org www.boxerworld.com www.gsdca.org www.petfinder.com www.terrificpets.com