The Red Rooster to answer your question about size. It looks like you have a "pure" NN but is she a bantam or standard size. The bantams are usually mixed with other breeds to attain size. So the bantam size varies according to the mix. And actually the standards are frequently a mix also. In my experience, which is not hugh, the males standards are usually very large half their females . And when you compare them to the males they look sort of small. But at the present I have a females that is over five pounds which means that she is not small for a hen.
So tho really answer your question about size...............it depends on the parents
chickgrowerdan Nice parents/ nice splash. But what breed is the mother ? Looks like a blue Wyandotte or mix thereof : some orpington ? father is a handsome