How Can I Tell If A German Shepherd Pup Is Full Blooded?

Do you have your AKC registration application or will one be given to you after you provide your breeder with proof of spay/neuter per your contract or anything? If pure bred is important to someone those papers are key (not papers from a 'paper' or pet registry which is often considered more likely your pup may not be pure bred or there were ethics problems often involving lineage with AKC at some point and the breeder could no longer register with them). You can have your pup DNA matched to Sire and even Dam if it's a concern. There are some commercial 'what is my puppy' DNA breed tests but not all labs have all DNA, and they also don't work the way people think they do and also aren't accurate at this time so are more for entertainment value at this point. They may get it eventually but right now they pick up on other things and give hilarious results (especially when lineage is known and proved and dog was tested for fun) more often than accurate ones.
www.gsdca.org
www.youtube.com
www.dogfoodanalysis.com