I think it's a very nice rifle. I have examples by both Henry and Alvin but I'd never heard of Nathaniel. Both Henry and Alvin had very long working lives, perhaps Nathaniel didn't...or he may have worked with either of his brothers and thus we don't see his name anywhere near as much.
I also have one of those mystery NE rifles...signed "W. Allen". Presumably a relative of the better known Silas Allen but, as yet, I haven't seen any reference to him.