Hi Nathaniel As I've said in other posts, the only way to be sure that a dog (of any breed) is purebred is if they have registration papers from the AKC or a similar organization. This proves that their parents were purebred.
However from the photos your puppy certainly looks like a Rottweiler, and from what I can tell he appears healthy. It's impossible to judge from photos the accurate size of a pup/dog as the photos seem to distort that. But if you use my Rottweiler Puppy Growth Chart you'll be able to see how he compares to the 'average'.
Do bear in mind that every pup is different, and the majority aren't average. Some will be bigger, some smaller, some will grow faster than others, end up with slightly different proportions etc. As long as your little guy is happy and healthy, that's the most important thing.
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