As compared to the NP5, NP10, NP10N, more time is spent in the hand graduation work of the top and bottom plates. Skillful handwork is combined with quality well-aged European materials making this instrument unique at this price point. The NP15N also has a pure hand-rubbed Italian oil varnish finish in a light antique style. As with the NP10N, the use of a pure oil varnish improves tonal quality and will help protect the instrument for many generations. Oil varnishes hold up much better, breathe better, and are the traditional varnish used by the old Italian masters.