Hello Wendy the " N " letter you see, could be either, the makers mark or the date letter but because you do not mention any other hallmarks in the ring, and because you say the N is on its side, it will probably be the maker's mark.
It's going to be tough one, trying to identify the maker, if there are not other markings.
You can date the ring to large extent, by examining the subject matter of the cameo and the material the cameo is made from, providing the cameo is original to the ring setting. You can find information on antique cameos here.
