This is the highly regarded "long-nose" or "pancake" version of the 50mm f/1.8 AI-S Nikkor, depending on the specific international market variant. Identified by its serial number in the 2 million range, this is a Japanese-market version of the slim AI-S lens. It features a minimum focus distance of 0.45 meters and the high-quality Super Multi-Coating (SMC) characteristic of the era. The AI-S mounting system allows for linear aperture control, which was essential for the "Program" and "High Speed" modes on Nikon bodies like the FA or the N2000 we previously cataloged. It is famous for being one of the sharpest 50mm lenses Nikon ever produced, combined with a remarkably compact physical profile that makes it a favorite for travel and street photography.