Abbreviation: N = "Nano Crystal Coat" (Nikon)
The abbreviation N means "Nano Crystal Coat" and is seen on Nikon products.
Explanation from Nikon
Nano Crystal Coat is an antireflective coating that originated in the development of NSR-series (Nikon Step and Repeat) semiconductor manufacturing devices. It virtually eliminates internal lens element reflections across a wide range of wavelengths, and is particularly effective in reducing ghost and flare peculiar to ultra-wideangle lenses. Nano Crystal Coat employs multiple layers of Nikon’s outstanding extra-low refractive index coating, which features ultra-fine crystallized particles of nano size (one nanometer equals one millionth of a mm). Nikon now proudly marks a world first by applying this coating technology to a wide range of lenses for use in consumer optical products.
See examples of effected products
 | Nikon AF-S 14-24mm F2.8 G ED |
 | Nikon AF-S 24-70mm F2.8 G ED |
 | Nikon AF-S 70-200mm F2.8 G IF-ED VR II |